That NY Times article basically said the same thing, they are alienated and excluded from society, hence the anger. Forget the fact that Muslims feel superior to all others to the point that they should kill all non-believers. Nor that they are not acting out like a high school shooter-shunned and outcast (as well as mentally defective). Rather, they are happily killing for their religion, and many others are celebrating it.
It is amazing how they just don’t get it.
These bloody morons want a world wide MUSLIM Caliphate; with EVERYONE being their kind of Muslim. Because Sunni will fight Shia and vice-versa to the bitter end.