Anne's got a couple of links to recent articles and statements comparing Ahmadinejad to Hitler. The comparison between the two men holds as far as it goes, but in terms of global culture there are at least two significant differences between 2006 and 1939. The first, of course, is that the world ought to know better than to discount the ravings of a genocidal maniac threatening to wipe out millions of Jews. The second, of course, is that there's no doubt that there are tens of millions of people all over the world who do know better. Anyone who doesn't believe that Iran is nuclearizing with the intention of committing mass genocide is either willfully ignorant or stupid.
Six years after 1939, it was unacceptable to suggest in polite company that the Jews had the Holocaust coming. If Iran nuked Haifa and Tel Aviv tomorrow, a week would not pass before a European newspaper or intellectual made the "controversial suggestion" that Israel was "partly" responsible. They won't say it (just) to be controversial - they'll say them because they believe it.