I'm not saying any of this is a good thing, btw. Its just an observation.
9/11 - a couple of Muslims fly a few big-assed planes into the NYC World Trade Center. It blows up. A few thousand Americans are killed.
Since 2003, Americans have killed civilians in Afghanistan as it futilely chases the ghost that is the Taliban (dejavu Vietnam?). Collateral damage, says the USA. It happens.
People kill people. Whether you're the terrorist or the hero, the only difference is which side of the bullet you're on.
Perhaps there is no altruistic greater good. Its just war.