You're all right, this thread isn't going to go anywhere but bad.
The thread will only go bad if we make it so. So don't. Back on topic:
Undeserved, yes. Noone deserves attacks aimed at civilians. Unprovoked, though? Hardly. The United States as a country is definitely not innocent.
The thing is though, the attacks were not the act of a state that was feeling threatened, in which case the Pentagon part of the attacks might actually have been "legit" according to current US policy since it's a military target. And it would have been just as legit for the US to retaliate with overwhelming force afterwards. But rather, they were the act of terrorists, doing it not out of a need to defend themselves but simply out of a desire to cause as much harm as possible. And that is
never justified, even though the US has indeed done some extremely shady things in its past that had provoked them (and in the case of these guys, trained and armed them).
As I see it, it comes down to the difference between military action and terrorism. Military action against military targets is called war, and it goes on between two or more countries. And the aim of military action is not to kill as many people as possible, but just to destroy the other party's ability to make war on you and/or gain some land/resources/advantage, which in some twisted kind of way makes it "ok". We'd prefer it never happens of course, but that's utopian given the state of the world today.
But terrorism is not aimed at military targets. It's not aimed at preventing danger to yourself, your country, your family. and it certainly does not gain you any benefits. Hell, it does the opposite on all those counts. It's just aimed at causing as much pain and grief as possible to the most vulnerable target available. And that is what makes it so very, very wrong, regardless of what reasons the perpetrators may be citing for their acts. Reasons, in this case, just don't matter, because the only true reasons are hatred and revenge - Neither of which are ever brought to bear on the actual objects of said hatred and revenge, but on whoever happens to be an easy target.