Columbia President Bollinger scolded Iranian President Ahmadinejad's denial of (or on Ahmadinejad's account, at least to Western audiences, questioning of the evidence for) the Holocaust on the ground that this denial (or questioning) is factually preposterous: The Holocaust, Bollinger noted, is extraordinarily well-documented historical fact.
Fair enough, but the assertion of factually preposterous views (or even the questioning of extraordinarily well-documented facts) is not ordinarily denoted a moral failing. In the United States, millions of citizens disbelieve the extraordinarily well-documented scientific fact that human beings evolved from other species. Three of the out-and-out evolution deniers are candidates for the 2008 Republican nomination for President and President Bush himself has said that "the jury is out" on evolution. These are preposterous views, to be sure, but not the sort of thing that would get you imprisoned for espousing in Germany or Austria.
Holocaust denial is not a crime in the former Third Reich merely because the Holocaust is an extraordinarily well-documented fact. It is a crime because it so often is a view espoused by neo-Nazis. Likewise in western countries that do not criminally punish Holocaust denial, its offensiveness stems largely from the likelihood that someone who denies the reality of the Holocaust may very well wish to repeat it.
Exactly why a neo-Nazi would want to deny, rather than celebrate, the Holocaust, is not entirely clear, but probably has something to do with the fact that literally promoting genocide could lead to imprisonment in countries with less speech-protective notions of incitement than the United States. That can't be the whole of the story, however, because even in the United States, where "abstract" expressions of sympathy for the Nazi program would be protected by the First Amendment, anti-Semitic groups such as the Aryan Nations deny (or question) the Holocaust. Their evident goal is to demonize Jews for spreading the "myth" of the Holocaust. Thus, here, as in Europe, Holocaust denial is a marker for neo-Nazism (and associated ideologies).
Holocaust denial (or questioning) by strongly anti-Israel figures such as Ahmadinejad is most clearly meant to undermine the legitimacy of the State of Israel, which was created in part as a refuge for Jewish Holocaust survivors. To be sure, Ahmadinejad and others also say that the Holocaust does not legitimate Israel because victims of a European crime should not have been compensated by the displacement of Palestinians who, for the most part, did not participate in that crime. (Ahmadinejad would describe Palestinians as completely innocent but I say "for the most part" because some Palestinians, including Mufti Haj Amin al-Husseini did try to assist Hitler.) In general, the argument that one set of innocents should not be made to suffer for the sins of others has considerable moral force, which leads one to wonder why Ahmadinejad et al feel the need to supplement this prima facie plausible argument with the completely implausible claim that the Holocaust is a hoax. And that in turn leads one back to the usual explanation for Holocaust denial, namely sympathy for the Nazi program.
(Just to be clear, and in the interest of avoiding extended discussion on this tangential point in the Comments, I am NOT saying in the preceding paragraph that the displacement of Palestinians in 1948 means that Israel is today or ever was an illegitimate State. I AM saying that this argument at least has some theoretical force to it, while the "argument" that the Holocaust is not established fact has no force to it whatsoever, and thus leads one to worry about the motives of anyone who makes it.)
Posted by Mike Dorf