I cited also the fact that Muslims react more violently to perceived insults to their religion.

This is not something we can say with any certainty. For one thing, we can't attribute the backlash to the cartoons as being entirely a response to an insult to Islam or the Prophet. There are many socio-economic factors that also have to be taken into consideration. A big part of the backlash was a response to perceived discrimination against Muslims in that context, and it still is. Secondly, I have seen reports of other religions reacting violently to perceived insults to their religion. There are numerous cases of a violent backlash among extremist Jews because of perceived insults to the Jewish religion, as well as death threats and even the Jewish equivalent of a fatwah. And I have seen cases of Christians doing the same. Hindus have also committed numerous acts of violence against non-Hindus, and I don't think we can say with any certainty that none of them were a response to perceived insult to their religion. The only difference is that when these things are committed by groups other than Muslims, we just don't hear about it very often. Our media tend to put a lot more effort into publicizing violent acts by Muslims than they do into publicizing violent acts committed by other groups.