Regarding intelligence agents not killing people: what about Bond?
As for intent, just let me tell you a fact about Portugal. One of our national heroes is a baker. The story goes like this: after being routed during an attempt to invade us, a few Spaniards hid away in her oven. When she came to work, she found them and finished them off with her baking shovel. Now, this was a long time before the Genebra Convention and I don't support her actions towards enemies that were already defeated, but when you invade someone's country you are bound to find resistance from both civilians and military. I don't know much of American History but similar episodes must have happened during the Independence War. The intent, then as now in Iraq, is to defend your country from invasion.
But is terror a legitimate means to that end?
The Macmillan Encyclopedia defines terrorism as "The use of violence and intimidation to achieve an objective that is usually, but not always, political". It seems to me that all acts of war, as well as 'muscled diplomacy' (comprising the idea of an ultimatum) fit to this description. So, keeping to this strict definition, everybody, from states to playground bullies and parents disciplining their children, does it. We're all terrorists; as a noun, it could replace 'mankind'.
Though technically useless as a way do discriminate between people, the term is still widely used. Why? Because it questions the legitimacy of the other guys - generally the weak ones - fighting back. I recall that when we, the Portuguese, were fascist and the oppressors a good chunk of Africa
the term 'terrorism' was used to designate the same guys that, by the standards of the international community, were freedom fighters. It's a dirty name, that's all. You call it to people you don't like. Especially if you are oppressing them and they have the nerve to fight back.