Problem with that is if you kill the bastard...then he becomes the rallying cry for jihadists everywhere to come here and avenge his murder.
They don't really require any excuses. They're going to murder and terrorize without them. I understand your point, but I don't think jihadists care one way or the other. They're going to do what they've always done, what they're trained to do, in numbers, as many times as possible, until or unless they are completely neutralized one way or the other.