I have only just read the whole of this thread; it is heartening to read so much reasoned and heartfelt discussion of this terrible act. I have said before, (and often cited the dreadful things done, in the past, in the name of Christ), that when people are so convinced, by blind faith, that they are right and everyone else is wrong, there is no reasoning with them.
This applies to fundamentalism and totalitarianism of all types, and is why it is so frightening when we are faced with people who cannot prove, or argue, but insist their way is the only way, like IS.
If we say that the satirists were creating trouble, and should have been stopped, are we not giving in out of fear? But then, we are right to be afraid, for all the reasons above. Religions, or what men have done in the name of religions, have much to answer for.