I was replying to aleph_1’s comment:
You did not answer my question. What argument of yours is confirmed by Hitchens? Please quote and explain.
The article in Wikipedia Criticism of Holocaust denial seems a good starting point to evaluate the credibility of various arguments and counter-arguments.
If David Irving, or any daring author, truly wanted enough attention, he could try touring Russia promoting an expose’ that proves Vladimir Putin is behind the murder of journalists. Testing the limits of free-speech in the West is relatively safe, by comparison.