One thing I find common with racists, especially the extreme not-righ-in-the-head ones is this: They're failures (real or imagined) in life with no skill, achievement, work, or duty they can be proud of, so they decide to latch on their heritage, saying that they're superior because they're born that way. It doesn't matter if the racist himself is caucasian, oriental, african, or whatever--it always boils down to them believing that they deserve respect for something they did not earn or work for.
As for Holocaust deniers--well, there are still people out there who say the world is flat, and that babies come from storks.