How about the school kids who shoot people or commit suicide as a response to relentless bullying? Do the bullies bear no responsibility for provoking violence and self destruction through their campaigns of harassment and insult?
Do you not appreciate the distinction in your own analogy? You are giving examples of provocation of a particular person. A religion is not a person. It is a set of beliefs held by any number of people. Was Pam Gellar et al. seeking to provoke a particular follower of Islam? Say Said of Damascus? The everyone draw Said contest? Of course, not. General provocation is a feature, not a bug, of free speech. Come on, the Islamic tenant that there is only one God and his name is Allah and Mohammed is his messenger is quite provocative to followers of other faiths. For a start, Islam denies the divinity of Christ. To a believing Christian, that's extremely provocative and offensive. If we were to curtail general provocation lest we cause offense, then the world would be a very boring and miserable place. Trey and Matt would be ostracized, sued, or in jail. Look how they provoked this guy: http://www.capalert.com/capreports/southpark.htm