Hustini -- think of it this way. A lot (though certainly not all) of the Arab world are like blacks in America. Just as when a white cop shooting a black kid makes people go ape$#@! crazy, there are people who have blood in their teeth and $#@! razor blades if some Westerner takes out a fellow Muslim as a so-called terrorist target.
But Muslim-on-Muslim violence is often treated a bit like black-on-black violence in the U.S.: it just doesn't register much of any outrage or importance, even if they're a 100 times more likely to die by the hands of a Muslim brother than by a Westerner. It's like a sort of tolerance for "We can screw ourselves over ad infinitum, but don't you dare come in here and follow our example."