There are no facts you can tell the leaders of Iran that they can't
google themselves, if they just visited a neighboring country that had unrestricted Internet access. When they
hold an event questioning the holocaust the correct response is not to hold an event to "counter it". To do so is to miss the point. When they hold an event such as this they are trying to piss you off. It is not about researching the most well documented event in human history, it is about hating you.
Here are two responses that are better than getting upset.
1. Ask world Jewery to set aside one minute of today yawning. As in - who cares what kind of bigotry they exhibit in Iran. You have to be an upper-East Side New York liberal Bush hater to still find it surprising that Iran hates Jews. When Bush put Iran in the axis of evil, it is because the Irani leadership really are bastards, not because Bush just needed a third country to not like.
2. Piss Iran off yourself. Hold a conference - "Iran, is it really there?" or "Islam - the billion most gullible people on Earth" or if you were feeling charitable "Crisis in the Muslim world: The obvious reason why they have produced no historians of note - ever"
(Be prepared for a few days of rioting)
Even
Palestinians will be banned if they are not toeing the party line here. As an old activist once said, if someone calls Jews dogs, would you hold a conference that provided unequivocal proof that dogs have tails, and Jews don't, and dogs bark, and Jews speak a human language, dogs walk on four legs and Jews on two. . .? If someone calls a Jew a dog, they are not making a biological point. If someone challenges the historicity of the holocaust, they are not making a historical point.
The Weisenthal center is dignifying this sort of hatred with a response because they need to show that (1) Iran is not evil in any way that can't be corrected with a simple conference, that this is about ignorance, not hate, and (2) so that the Weisentahl center can claim to actually be doing something about this.
But despite what "education theorists" have been saying for decades, you can't just teach someone something and expect them to be the way you want. Virtues such as those it would take to make Iran our friends have to be inculcated over a long time with the proper upbringing for a whole generation of leaders. This will not start with a conference. A conference shows that you take them seriously - which you shouldn't.
The Weisenthal Center justifies its budget on the grounds that it does something about anti-semitism. Well, perhaps here the best thing to do is nothing. Somethings are just not meant to be taken too seriously. The best way to respond, is to find a disincentive for Iran to do this. It has to be made to be not worth it for Iran, or Iranians. But this is too hard, so the Center is just doing the next best thing, which is actually not a good thing at all.