Holocaust Deniers

Reuters reports on one of the participants in Iran's holocaust conference:

Among the participants was U.S. academic David Duke, a former Louisiana Republican Representative.

He's an "academic"??!! I can only assume that the Reuters reporter did not know who he was and simply used the information provided by the conference organizers.

Holocaust Denial

Iran is holding a conference on holocaust denial. Sounds odious, obviously, but it raises a question I've often wondered about: What exactly are holocaust deniers denying? Do they deny that there were any concentration camps at all? Are they quibbling about the numbers who were killed? I suppose there is probably some variation. But I would like to pin it down a bit more, so I could better understand the people involved.