@salima,
Here is a paper arguing that the founding fathers of America among other sympathetic groups, such as those who resisted Nazi occupation, were terrorists by the current legal definition used in the United States:
George Washington was a terrorist
Some of his side points are pretty weak, a law against terrorism doesn't make sense given a law against being one who engages or has engaged in terrorism. I would also say that the Nazi parallel is in bad taste and follows in the tradition of drawing such parallels lightly for shock value/rhetorical convenience.
It all comes down to pragmatism. If the terrorist is working for goals that conflict with yours, you certainly should consider him or her a dangerous enemy to be stopped by force. My goal as a United States citizen and as a human is generally to stay alive. I am willing to see killed those who would kill me to prove a political or religious point. Period. It doesn't matter to me if there is some aspect of their struggle that I can relate to; I would still put not dieing at the top of my priority list. This might be different if their goals and mine do not conflict, that is; if my ultimate goal were, for instance, the freedom of my people, it is conceivable that I might be willing to die for my chosen cause. Fortunately I am not in any such position.
I might also note the lack of British civilian casualties (as far as I know, not including those born in America who were technically British citizens) during the revolutionary war. I think that there is some distinction to be made when civilian targets are made fair game.