Looks like, among other things, he was that, at least near the end of his life. 
HR vol. 15 no. 3 (May / June 1995), pg. 46: In a letter, Martin writes, "Personally, I am about brimful (sic?) on 'gas chambers' and may stop reading about the subject. As I have mentioned, I classify them with unicorns; for centuries Europeans have believed tenaciously in the latter since at least the time of Aristotle, but in all that time never came up with one. Maybe there will be centuries of belief in 'gas chambers' with the same consequences. I am sure the 'hoax Establishment must stick by this fantasy, for to admit that it is all smoke would seriously undermine faith in anything else they allege. However, they did slink off from the fable of soap made from Jewish fat..."
One letter of Martin's which is available online appeared in JHR vol. 12 no. 2 (Summer 1992), pg. 251). In a letter entitled "Reflections on a Death," Martin writes about the Holocaust, "...the Holocaustians have turned the whole thing into a new religion anyway. To me there is a close relation between a racket like this one and spiritualism, for example. Holocaust zealots trap their revisionist critics in much the same way that the spiritualists treated their scoffers during their heyday...The 'Hoaxers' do much the same thing: the more outrageous of the Holocaust atrocities they endlessly circulate don't have to be proven. Instead, it is up to those who deny they happened to prove they did not...One of these days I should try to get a foundation to underwrite a trip to central Africa. After returning I would announce that I had encountered a tribe of talking monkeys, and then challenge anyone who does not believe me to prove otherwise." (See: http://www.ihr.org/jhr/v12/v12p245_Letters.html#Martin)
(above from ). That, and spending 25 years hanging out with IHR puts at the very least a serious taint of holocaust denial on his fascinating resume. ∇∆∇∆