One obvious way to deny the Holocaust is just to say it didn't happen, or wasn't really so bad (see the infamous Robert Faurisson as commented on by Oliver Kamm). But there are other more insidious and pervasive forms of Holocaust-denial. Saying that Bush = Hitler is one such. If Bush is as bad as Hitler, then it follows that Hitler was no worse than Bush. Since Bush is the elected leader within a liberal democracy, this amounts to saying that Hitler had a similar kind of legitimacy. And it amounts to saying, also, that he did nothing worse than what has been done by Bush and his administration, say in Afghanistan or Iraq. So far, the highest claim I've come across about innocents killed in Iraq stands at some tens of thousands. Suppose this figure to be accurate. To claim that it is remotely equivalent to what Hitler and his regime were responsible for is to claim that Hitler and co killed something of the order of tens of thousands of innocents. Even David Irving might agree with that.
If only it were true.
Similarly to say that what America (or Israel) does is no better than what the Nazis did (see here, here and here - and there are many other examples) is to say that what the Nazis did is no worse than what America (or Israel) does. That's what identity relations are like: if A is the same as B, then B is the same as A. And until there's some evidence that America, or Israel, or the Bush administration, or the Sharon government, is setting up factories of death in which millions upon millions of members of hated ethnic minorities (or even majorities) are deliberately and hideously tortured and killed, then claims that America or Israel is equivalent to Nazi Germany will amount to ways of denying or diminishing the fact and the horror of the Holocaust. (Eve Garrard)