From what I recall, if you provoke someone to attack you, you're to blame in that scenario, legally speaking.
An by "provoke" I mean "directly and intentionally." Or at least that's what it should mean. I could be talking out of my ass though.
So stuff like "Your mother sucks cocks in hell" right after that person visited a funeral for their mother? Totally your fault.
Stuff like "*walks like a gay person*" is not your fault.
Of course, that doesn't excuse murder, and it doesn't excuse the reaction to previous Quran burnings.
Too many people, like that egotistical priest, seem to think that free speech means "I get to say whatever I want, and you don't get to say anything bad about what I said."
By definition, free speech cannot violate free speech.
As far as book burning itself goes, I oppose it on the principle that it's a form of censorship of ideas.