The only time I would ever burn a book is to keep warm in a freezing blizzard or to cook food if there is no other fuel available. I would never burn a book, any book, even one's I violently disagree with, for a political point. Even very horrible books, like Hitler's Mein Kampf, should be preserved, mostly for historical purposes and to give an insight into his madness (anyone who tries to claim that Hitler wasn't a blood-thirsty genocidal maniac can be proven wrong with just a couple of pages out of Hitler's own writings). Racist books should be preserved (not promoted) in order to preserve our knowledge of the past's culture. If anyone tries to say "hey, the Confederacy wasn't that racist", we can just point to the crap many in the South were publishing and reading as evidence that "yes, the confederacy was filled with slave owning racist berks".
I think that really awful, hatefilled books should not be promoted or mass printed, but they should be preserved to remind us of what we used to be, and how we have and can change. Once you start saying that some books can be removed or destroyed, you open yourself up to the demolition of history itself. Mein Kampf is an awful, awful book (in terms of subject matter and writing style), but it's a useful reminder of how crazy the Nazis were and how awful Hitler was.