As for conspiracy theories. I am happy to acknowledge I've been completely brainwashed by "the system":

We did land on the Moon in 1969, and we made several return journeys in the following years.
The universe is approximately 13.787±0.020 billion years.
Evolution is certainly happening, as evolution is nothing more than changes in allele frequencies over time. Evolution by natural selection is the best explanation for the diversity of life today.
We are related to dinosaurs (and birds are dinosaurs) but more close to apes; specifically, chimpanzees and bonobos. We are also more distantly related to plants.
Condensation trails (contrails) are the result of water vapor that results from the burning of hydrocarbons.
Traditional medicine that has been demonstrated to work is called medicine.
All atheists are wrong about some things, and some atheists are wrong about many things.
Vaccines work, and they work really well. The most significant issue with them is that they require action before an infection takes place, and therefore requires positive action by the individual or parent. As a very small percentage of vaccines cause significant side effects, some individuals will be harmed and the question would be, would the individual harmed have been "okay" had the vaccination not taken place?
Seat belts work, and they work really well. The most significant issue with them is that they require action before an accident takes place, and therefore requires positive action by the individual or parent. As a very small number of accidents cause harm that would have been otherwise avoided had seat belts not been worn, some individuals will be harmed and the question would be, would the individual harmed have been "okay" had the seat belt not been worn?
Wearing masks during the COVID pandemic saves lives.
The Holocaust.
The Earth is a sphere.

Some concepts I disbelieve due to lack of evidence:

Loch Ness monster or Big Foot.
The QAnon conspiracy theories.
Chemtrails.
A 6000-year-old Earth.
The benefits of organic foods (I prefer not to eat organic food, if and whenever possible).
Any traditional Chinese medicine.
Homeopathy.
The foundations of chiropractic medicine.
ESP.
Facilitated communication.
Vaccines cause autism.

The Holocaust

I am disheartened that it's necessary to address this, but indeed, the Holocaust was as real as documented and as horrendous as described, regardless of any misinformation circulating on platforms like TikTok or other social media.

Following World War I, a significant portion of Germans faced impoverishment. The Treaty of Versailles imposed harsh terms on Germany, including territorial losses, military restrictions, and reparations payments, contributing to political and economic turmoil during the nascent Weimar Republic. Many perceived this treatment as unjust and sought any solution to the economic and military collapse of the former German Empire. Consequently, when politicians from the Weimar Republic signed the Treaty of Versailles, this new form of democratic government lost legitimacy in the eyes of numerous Germans, spanning both the left and right political spectrum. The economic burden placed on the Weimar Republic by the treaty forced the government to print money just to pay its internal debts (the repatriation payments had to be paid in gold), resulting in a hyperinflation that devastated the German middle class. In response, populism found fertile ground for its leaders. However, populism is perilous as it peddles the simplistic and often false notion that complex problems have easy solutions.

Populist figures like Adolf Hitler attributed Germany's defeat in World War I to traitors who supposedly stabbed the nation in the back (the Dolchstoßlegende or "dagger thrust legend"), despite Germany already facing setbacks before the Armistice was signed on November 11th. After the war dragged on for two-and-a-half years with no end in sight, Germans constructed the heavily fortified Hindenburg Line behind their front lines, retreating to it at the onset of Spring 1917. This formed an impenetrable barrier for the Allies for the subsequent year. Although the Germans launched a series of successful attacks led by stormtroopers at the beginning of Spring 1918, penetrating deep into Allied lines, they were eventually contained, suffering heavy losses and forced to retreat back to the Hindenburg Line by August. The line was breached by Allied forces on September 29, 1918, leading to a full-scale German retreat over the following month and a half (see a day-by-day summary of events in this YouTube video). Populists, however, claimed that the German army, had they not been betrayed, could have held out, possibly even repeating the successful assults of the Spring Offensive leading to the defeat of the western Allies (after all, they had just defeated Russia and then the Soviet Union the previous year). They attributed blame to the politicians involved in the negotiations leading up to the Treaty of Versailles, accusing them of betraying Germany's interests.

Additionally, Hitler propagated the notion of German racial superiority (labeling Germans as being of an Aryan race), asserting that Germans and other Nordic peoples were superior biologically, intellectually, physically, and morally to other races, especially Jews, Romani people, and Slavs.

Furthermore, Hitler presented Germans with an existential threat from the East: the communists of the Soviet Union. He pledged to defend Germany against this threat initially and subsequently conquer it, offering Germans Lebensraum (or "living space") for German colonists to settle and prosper. He also provided Germans with a scapegoat against whom they could vent their frustrations and anger, specifically targeting Jews, but including others, such as the Roma, Sintia and Polish.

When Hitler gained absolute executive power with the passing of the Enabling Act in 1933, within two years, he stripped Jews of most of their rights. Some of the provisions in the Nuremburg Laws included:

The stripping of citizenship, rendering them stateless and depriving them of other legal rights and protections.
Restrictions on marriage and even sexual relations with any person of Aryan descent.
Exclusion from any civil-service occupation and many professions, and for other professions and occupations, they were often subject to quotas.
Exclusion from the education system, forcing Jewish children to attend underfunded special Jewish schools.
Exclusion from public spaces possibly including parks, restaurants and theatres.
Segregation on public transportation.
Loss of property rights, with many Jews seeing their property and assets confiscated.
Imposition of censorship and restrictions on their freedom of speech and assembly.

According to the Nuremberg Laws, individuals with one Jewish parent were considered Mischlinge ("mixlings") of the first degree, and those with one Jewish grandparent were labeled Mischlinge of the second degree. Both of these groups faced various restrictions and lost privileges under Nazi rule. Nazi propaganda at this time portrayed Jews as:

Subhuman, being racially inferior, biologically degenerate, physically unattractive, morally corrupt and compared to vermin or parasites.
Enemies, traitors and subversives, working to undermine and destroy the German Volksgemeinschaft (racial community).
Scapegoats for all societal problems, including economic instability, political unrest, cultural degeneracy, Germany's defeat in the First World War, and the economic hardships of the Great Depression.
Demonic, malevolent, scheming, manipulative and conspiratorial, being simultaneously the masterminds of both capitalism and communism.

While discrimination against Jews was endemic up to 1938, actual acts of violence were sporadic and not centrally orchestrated. Groups such as the Sturmabteilung (the SA) and the Shutzstaffel (the SS) as well as others perpetrated acts of violence in the shadows, during the day, the campaigned against the Jews using boycotts, vandalism and legal persecution. This changed with the murder of a German diplomat in Paris in 1938 by a Jewish refugee, the Nazi government organized a nationwide pogrom against everything Jewish:

Jewish homes were attacked and vandalized.
Jewish-owned shops and businesses were looted.
Synagogues were burned.
Many Jews were assaulted, between one and two hundred were killed and many more were seriously injured.

This was called Kristallnacht (the Night of Crystals, referring to the broken glass that littered the streets around any property owned by Jews). Following this, Jewish adult men were arrested and many were now held in concentration camps. Concentration camps, initially, were used as prisons and as labour camps to aid in the war effort. Over the next few years, the conditions in these camps worsened, and many prisoners died of disease or malnutrition, but the purpose of the camps was primarily to provide a labor force to aid the preparation for war as well as lining the pockets of the Nazi officials. With the conquest of Poland, however, the decision was made to first restrict Jews to ghettos and from these ghettos, Jews were forced to work often with no pay. The ghettos were overcrowded and unsanitary, leading to many dying from typhus epidemics, first in Poland and later in the occupied Soviet Union. Over one thousand ghettos had been established in the East by 1942. In addition to the ghettoization of the Jewish communities, the Germans sent out Einsatzgruppen (or "task forces") staffed by thousands of members of the SS, who killed approximately two million, 1.3 million of which were Jews. Some Jews were however sent along with Polish, Roma and others to concentration camps, which were at first camps to provide labor, although the conditions where such that many died from starvation, exhaustion, beatings or executions. There was, however, one extermination camp that was set up in Poland in late 1941: Chelmno. Polish Jews from Łódź, as well as others, were shipped here, where most were packed into vans that were driven around until the carbon monoxide gas killed the occupants. This was not the industrial scales of mass murder seen after 1942, but still between 150 and 200 thousand were executed over the years this camp operated. After all, the liter or two of gasoline required to kill a truckload of Jews was much cheaper than the corresponding number of bullets, bullets that were required on the Eastern Front.

Up until the start of 1942, the war was going well for Nazi Germany, and thus it was decided to transition from using Jews for forced labor to outright extermination of the community as a whole. This began with the Wannsee Conference, where Reinhard Heydrich and Adolf Eichmann presided over a meeting of SS and Gestapo leadership, Nazi Gauleiters and other regional administrators, and ministerial officials from the Foreign Office, the Justice Ministry, the Interior Ministry, and the Ministry of the Occupied Eastern Territories. Together it was decided how to put into effect die Endlösung der Judenfrage ("the final solution to the Jewish question").

This would entail the establishment of additional camps like Chelmno, only now purpose built to swiftly and efficiently exterminating those who arrived at their gates. Some labor camps were repurposed to facilitate the rapid and systematic killing and disposal of arrivals deemed unproductive, including children, women, the elderly, and the infirm. However, these camps were not established within Germany, as some opposition still existed among the German populace and it would be impossible to hide what was happening. Instead, they were situated in occupied Poland where large tracts of land had already been cleared of their former denizens where the SS had absolute control. The trains that were previously transporting supplies to the front lines and returning empty were now filled with Jews and others from the Occupied Eastern Territories, destined for camps strategically positioned along the rail lines returning from the Eastern Front. With each boxcar of munitions and supplies dispatched eastward, an opportunity arose to transport a boxcar of Jews back to Poland. Adolf Eichmann, with his administrative acumen, played a pivotal role in making this logistical nightmare a reality. His analytical and methodical approach ensured the efficient delivery of as many Jews and other "undesirables" as possible to the camps. Upon the trains' arrival in the East to deliver supplies, Eichmann meticulously orchestrated the presence of Jews at the stations for the return journey, ensuring their swift herding onto the awaiting boxcars with minimal turnaround time. Over a hundred Jews could be crammed into a single boxcar in overcrowded and inhuman conditions. Schedules ensured that there was sufficient time to deal with one trainload before another arrived, otherwise it might be impossible to control those who knew they were next.

Eichmann operated with ruthless efficiency. If a train was scheduled to stop at an extermination camp, he ensured that those being picked up were old and infirm and orphans. Those Jews deemed capable of work were directed to labor camps, and if they had children and families, to ensure compliance, they were sent with the able-bodied parents, only to be exterminated upon arrival when there was no more opportunity to escape. It would not be surprising if Eichmann suggested even tighter packing of boxcars destined for extermination camps, showing little concern if some perished on route. Conversely, those destined for labor camps received slightly less inhumane treatment. He would not want his potential labor pool untimely reduced. Eichmann ensured the maximum number of Jews and other deportees were transported from the East as efficiently as possible, without impeding the flow of resources being sent back east.

This circuitous description of the organization of this killing machine is necessary, as the scale of the atrocities committed defies comprehension by any human mind. To grasp the magnitude, consider this: if you were to eliminate every person living in the province of Ontario, you would still need to find another million victims to come close. If you were to eradicate the entire population of Pennsylvania, you'd still need to locate another three million victims. Even if you were to exterminate every person in Bavaria, you'd still need to eliminate a third of those residing in Baden-Württemberg. To approach the staggering number of lives lost, you would have to execute everyone living in countries such as the Netherlands, Zimbabwe, Ecuador, or Cambodia. For context, Pol Pot's regime managed to kill two million Cambodians in the span of four years. This perspective may also shed light on why Israel went to such extraordinary lengths to capture and bring Adolf Eichmann to trial. For a dramatized portrayal of this event, you may be interested in watching Operation Finale.

While six million Jews were killed, along with 4.5 million Soviet citizens, 3.5 million Soviet prisoners of war, 1.8 million Poles, and one million others perishing at the hands of this state apparatus. totaling over 17 million.

The extermination camps were designed to offload the prisoners loaded into the boxcars and take them immediately to a place of execution, usually a gas chamber capable of holding up to 1000 prisoners at a time. Then the bodies were either buried or burned, although most bodies that were buried were subsequently exhumed and burned to try to hide the crimes that were committed.

700,000–900,000 were killed in Treblinka.
434,508–600,000 were killed in Belzec.
170,000–250,000 were killed in Sobibor.

Once the requisite number of people were herded into the gas chambers, Zyklon B, a pesticide that releases hydrogen cyanide when exposed to the air. After half an hour, the chamber would be ventilated and the bodies removed.

Many of the other camps were labor camps, where inmates were forced to work. In some cases, the inmates were given starvation rations, subject to arbitrary executions or beatings, worked to death or succumb to disease. Daily rations may consist of two cups of coffee for breakfast, four cups of vegetable and grain soup for lunch, and half a loaf of bread and a protein equivalent to a handful of peanuts (about 25) for supper. Two labor camps had the machinery required for exterminations, as well, so those prisoners who arrived and were deemed fit were put to work, while all others were generally sent to the gas chambers. Periodically, working prisoners were inspected for fitness, and those deemed unable to work were also sent to the gas chambers. There were only two such camps, but one is the most infamous:

1,080,000 million were killed in Auschwitz.
78,000 were killed at Majdanek.

At Nuremburg, Rudolf Höss, the commandant at Auschwitz, had submitted the following to the tribunal:

I have been constantly associated with the administration of concentration camps since 1934,

serving at Dachau until 1938;

then as Adjutant in Sachsenhausen from 1938 to 1 May 1940,

when I was appointed Commandant of Auschwitz.

I commanded Auschwitz until 1 December 1943, and estimate that at least 2,500,000 victims were executed and exterminated there by gassing and burning, and at least another half million succumbed to starvation and disease making a total dead of about 3,000,000.

This?figure represents about 70 or 80 percent of all persons sent to Auschwitz as prisoners, the remainder having been selected and used for slave labor in the concentration camp industries; included among the executed and burned were approximately 20,000 Russian prisoners of war (previously screened out of prisoner-of-war cages by the Gestapo) who were delivered at Auschwitz in Wehrmacht transports operated by regular Wehrmacht officers and men.

The remainder of the total number of victims included about 100,000 German Jews, and great numbers of citizens, mostly Jewish, from Holland, France, Belgium, Poland, Hungary, Czechoslovakia, Greece, or other countries. We executed about 400,000 Hungarian Jews alone at Auschwitz in the summer of 1944.

Other concentration (generally labor) camps include Arbeitsdorf, Bergen-Belsen, Buchenwald, Dachau, Flossenbürg, Gross-Rosen, Herzogenbusch, Hinzert, Kaiserwald, Kauen, Kraków-Płaszów, Mauthausen and Gusen, Mittelbau-Dora, Natzweiler-Struthof, Neuengamme, Niederhagen, Ravensbrück, Sachsenhausen, Stutthof, Vaivara and Warsaw. Each of these had satellite camps, so in total there were over 1000 concentration camps. Some of these camps also had gas chambers, but not on the scale of Auschwitz, Majdanek or the extermination camps. A shuttle bus driving between Mauthausen and Gusen vented the exhaust into the passenger compartment, capable of killing 120 prisoners with each trip before they reached their destination.

It is in this industrialization of execution that the Nazis were able to kill over 16,000 people a day over a period of three years. The Holocaust happened as described. Its numbers, while not exact, are not an exaggeration. It was Nazi propaganda that prepared the way for Germans to accept this treatment of anyone the government deemed unfit. By 1942, those youth in their early twenties had been exposed to dehumanizing propaganda for already one decade, almost half of their lives, and many were ready to follow through on the orders given by their superiors. The killing was calculated, bureaucratic, and systematic. Entire portions of the state government devoted significant time and resources to this final solution. German industry benefited from the cheap labor provided by these camps. In the end, 17 million people were killed, 6 million of which were Jewish, making up two-thirds of the pre-war population of Jews in Europe.

Flat earth

Flat earthers can easily help us understand why they believe in a flat-earth model if they can provide an actual model that correctly describes and justifies:

The angle at which the Sun rises and sets at different latitudes.
The path that the Sun and the Moon follow at different times of the year.
The path the planets follow in the sky.
The movement of the stars in the night sky, both throughout the night, and the changes throughout the year.
The change in angular diameter of the Sun throughout the day (almost none) and throughout the year.
The change in the angular diameter of the Moon throughout the month.
Both solar and lunar eclipses.
The seasons.
The apparent time it takes for both ships and aircraft to travel between specific destinations.
The paths and flight times taken by aircraft as they travel long distances.
The fact that as a ship leaves a port, it does not disappear to a point, but rather, the ship drops below the horizon long before it should still be visible.
Why my friend, a sniper, cares about the Coriolis effect when reaching out and touching something at two kilometers.
The tides.
Gravity.
Satellite communications.
GPS.
The various trips to the North and South Poles.
The ability for NASA and other space agencies to make such excellent photography and movies of the Earth from space.
Stellar parallax.

If the model contains a political component, then the person should also justify why all the governments in the world are colluding, why so much is being spent on this and how the governments feel this is necessary, and why no politician has ever brought forward any evidence of such collusion.