In my country (which just so happens to be a muslim country) people say that these mass extremist groups were hired by other people/governments/terrorist groups/whatever to make Muslims look bad. *shrugs*
I'm not saying that, but even though I'm not a muslim, I know enough about the religion to say that they're not actual muslims (as in people who actually believe in allah or shit) - in islam, you don't physically fight unless it's the last freakin' option and you have no other choice. In fact, this religion is freakishly peace-oriented, believe it or not. Killing was not called for here, obviously.
My opinion? This is kinda the same as a "Christian" going batshit insane if someone drew a lame ass comic of Jesus. In my eyes, this is no different from the time some die-hard twishit fan killed a girl because she said she was team Jacob. Some idiot thinks he's all that and everyone else is wrong, and instead of trying to proove them right, just makes himself and whatever he believes in look bad. Move along, this happens everyday.