Dalrymple has long argued in favor of free will as the ultimate explanation of human behavior, as opposed to vast impersonal forces. He takes the same approach in looking for the ultimate causes of the recent attack on Lee Rigby by a violent thug in Woolwich, while acknowledging the enabling role played by Islamic extremism. From City Journal:

If ever there was an adolescent identity crisis turned pathological, this was it: Adebolajo felt that he was more morally responsible to abstract millions than to the people by whom he was actually surrounded. Alienation could go no further. And needless to say, it was accompanied by a grandiosity that would have been absurd but for its ultimate effect.

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What these cases show is that it is not Islam that makes young converts violent; it is the violence within them that causes them to convert to Islam. The religion, in its most bloodthirsty form, supplies all their psychological needs and channels their anger into a supposedly higher purpose. It gives them moral license to act upon their rage; for, like many in our society, they do not realize that anger is not self-justifying, that one is not necessarily right because one is angry, and that in any case even justified anger does not entail a license to act violently.