Sidenote to the analogies in history discussion: IMO a much better analogy for terrorists in US history would be, say, Geronimo. By modern standards, he was a terrorist, he purposefully killed women and children. He also had a political cause and religious framing. *Lunatic*, n. One whose delusions are out of fashion.
I still say killing civilians for political purposes is unjustified: even if you're own people are getting ethnically cleansed, even if your own family was murdered by the invaders (as in Geronimo's case). Out of the Dark Age came the most magnificent thing we have in our society: the recognition that people can have a society without having a state.