Just a quick point, based on something I read in one of the comments threads: it is absolutely, positively, entirely unethical to invade a country and impose a government. Whether done in the noblest intentions or the most cynical, it is a betrayal of the right of a people and a nation to govern themselves... a right just as important as any that might be used as the justification for invasion.
To put this in perspective, this is exactly the same justification used by the Soviets when they invaded Hungary and Czechoslovakia- that they were "protecting the rights of the proletariat" within. The rights that the Soviets were purporting to be "defending" may have been different than the rights that the United States would be "defending" were it to invade Iran, Syria, or whatever, but the outcome would be the same. It is no different than the British citing their "white man's burden" back during the days of their empire, either; it is almost precisely the argument used in order to justify the British "mandatory" client-nation system that was largely responsible for the mess that is the middle east in the first place.
Of course, whether it's actually moral or not is probably irrelevant at this point, because this war has demonstrated the awesome power of the conservative spin machine to dominate and define the public discourse in the United States. The discourse in the rest of the world, of course, doesn't matter at this point. Still, it should be said.