I didn't say that all Holocaust deniers were not motivated by hate. I accept that a few of them may be, but I think not that many.
But why would you put so much effort into arguing a position, risking being hated by society and being prosecuted in the courts, just out of hate?
A slightly related example to show this is a similar argument that is associated with anti-semitism that I am sure that you will reject. Some conspiracy theorists like to point out the historical Jewish involvement in Communism. The usual argument goes that Communism was created and propagated by Jews (such as Marx and Trotsky) in order to gain revenge for anti-Jewish actions of the Russian people and the Czar, by inflicting this destructive ideology on Russia.
I can accept that Communism had a Jewish nature, but I seriously doubt that it was motivated by hatred of Russians. I imagine Karl Marx sitting writing his books, thinking about his ideas. He, as I'm sure you'd agree, wouldn't put all this effort in if he didn't believe in what he was writing. This would be his intellectual legacy.
LIKEWISE, I don't belive Holocaust deniers secretly think that what they are saying is wrong but come out with their arguments anyway, just because they hate Jews.