Why do they hate us?
From David Brooks's op-ed today,

But it could be that whatever causes they support or ideologies they subscribe to, the one thing that the killers have in common is a feeling of immense superiority. It could be that they want to exterminate us because they regard us as spiritually deformed and unfit to live, at least in their world. After all, it is hard to pull up to a curb, look a group of people in the eye and know that in a few seconds you will shred them to pieces unless you regard other people's deaths as trivialities.

If today's suicide bombers are victims of oppression, then the solution is to lessen our dominance, and so assuage their resentments. But if they are vicious people driven by an insatiable urge to dominate, then our only option is to fight them to the death.