I think John Robb has it exactly right. Those who frame the situation as a "war," or a "clash of civilizations" are falling into a trap. If it's a war, it's one that is never-ending, and actually can't be won. And will lead to oppressive, police-states. For an example of the kind of horrors that can be unleashed, please see the Bush/Cheney terror regime years.
How we frame the issue is really, really critical. And it is lazy and stupid to lump billions of people into one group. And it is false and not helpful. There are violent, malevolent people in the world. And small groups of determined fanatics can wreak lots of havoc.
We must do our best not to lose our heads in the midst of the terror. The pain and suffering seems unbearable, and it is, but we can't give in to fear. So yes, lets track down the transgressors. Let's punish the perpetrators, let's not take the bait of never-ending war.