Two more erroneous posts at the Volokhs and Prometheus argue it's wrong to call global warming denialists by that name, because it reminds some people of Holocaust "deniers", which reminds Volokh and Prometheus of Godwin's law, which somehow means then that "denialist" term is an ad hominem attack.
I would agree that the statement, "Global warming denialists are wrong because they're similar to Holocaust deniers," is an illogical, ad hominem attack. Count on me to shoot that statement down if somebody somewhere decides to say it. Otherwise, denialist is a fair and accurate term. "Skeptic" is inaccurate, and "septic," while sometimes accurate, interferes with talking to the other side. I and many others didn't draw the Holocaust connotation, and I don't really care if others noticed the similarity.
Generally, I'm a reluctant convert to the idea that we need to influence language. I'd rather have it be a neutral process, but that's not the real world, and the other side is pushing the other direction. The key is to be fair, accurate, and ethical. Denialist fits that criteria.
(More relevant musings by Connolley here. Ironically, he's one of the few tagged with seeing the Holocaust connection, but he doesn't use the term, preferring "septic" instead.)
UPDATE: I should clarify that I don't see anything ethically wrong with expressly drawing an analogy between the two denialist classes, but it's just that such an analogy doesn't prove anything. As a science matter though I wouldn't draw the analogy myself because global warming, while proven, is not as completely undisputable as the Holocaust.
UPDATE II: Adler at Volokhs repeats the claim some use denialist as a parallel to the Holocaust. His proof is Connolley, who doesn't use the term, and Pielke who says he proved it sometime around 2001, but doesn't provide a link.