He really did a convincing work on the montage and the voice-over, but NPOV must agree the majority of the video came from the deniers. Now I don't know how far fair use goes, but maybe they really have a case there. How did MST3K handle that?
None of which is any concern of Youtube. They have absolutely nothing to say about fair use or not. They follow the letter of the law as written and preserve their Safe Harbor protections under the DMCA. Youtube's actions are out of their hands on both sides unless they are willing to jump into the fray and assume liability.