That's my point: Why should people believe that it didn't happen in the first place?

For their arguments you'd have to look at their sites. Many of them are honest but simply mistaken, and others are anti-semites or neo-nazis. Your mistake is that you take it for granted that the Holocaust happened. If you take the scientific view, and take nothing for granted, you'll see that there is nothing particularly strange about other people coming to a different belief about things than you do. There are many examples of people who genuinely have mistaken beliefs, such as Duesberg who does not believe HIV causes AIDS, psychiatrists who think alcoholism is a disease, politicians who think socialism is good. And we need people who question standard wisdom, because sometimes those people are right, such as the person who first said the earth is round.

That is the reason why on some level I have more respect for Holocaust deniers who understand that propositions should be based on arguments and criticism, than I have for Holocaust believers who have nothing more to say than that everybody knows it and to question it is automatically anti-semitism. It's precisely this attitute, this presentation of the Holocaust as a belief rather than as a documented fact, that encourages Holocaust deniers to be sceptical of the Holocaust. Which is a shame, because the evidence for the Holocaust is overwhelming, and this simply needs to be pointed out. And if people still are not convinced this ought to be accepted.

And what would logically follow? a Jewish/Zionist conspiracy that has devised this fake history to take advantage of it. No?

No this does not logically follow. If it is a conspiracy it need not be Jewish, it could also be Allied or war propaganda or whatever. And they might argue that it doesn't have to be an organized conspiracy; it could simply be something many people happen to believe, just as many people happen to believe in God.

What would that make of Jews/Zionists in the eyes of these people?

You see, you keep using character arguments. The question of whether the Holocaust happened is a historical question which has been settled by arguments. Whether people might be anti-semites is irrelevant to what is true and what is false.

Aren't all that instances of antisemitism?

Those Holocaust deniers who believe that it is a Jewish conspiracy are probably very often anti-semites. But even then there is no logical contradiction between believing in a Jewish conspiracy and not being an anti-semite. Compare: if I believe that JFK was murdered by a conspiracy of men, that does not imply I am a sexist.

Henry Sturman