I have a recent edition of Fahreheit 451. In the back is part of an interview that Ray Bradbury gave regarding his work. The interviewer repeatedly tries to bait Mr. Bradbury into making negative political comments about the US and the war in Iraq and Afghanistan. And Mr. Bradbury repeatedly slaps him down.
After reading this interview, I'm pretty certain that Mr. Bradbury's anger toward Michael Moore isn't just about the title of his so-called documentary.
Fahreheit 451 = Fahrenheit 451
Good for Mr. Bradbury if he's pissed about more than just the title. Maybe if the title was use for something along the lines of the spirit or content of the book he would have been happier. Seeing as he is most likely and anti-communist it probably pisses him off to see a Socialist Piss Ant like Moore use his book's title.