Just a bit of refereeing the "debate." I say that with scare quotes because it isn't really a debate. There has never been a plausible moral case against the liberation.
1. A point of logic. The carping by the American left continues unabated. It is stupendous in its nonsense. Let's consider the claim, "Iraq had nothing to do with terrorism."
It makes no sense to say that Iraq had nothing to do with terrorism. It begs the question so blatantly that it should take your breath away when anyone whose job it is to consider these issues says this. Bush gave an argument that it does have something to do with terrorism. You can't just deny his claim without refuting his argument.
But you can't refute the argument: With an oppressed Middle East, the terrorists can win. But with a free Middle East living under rule of decent laws, they can't win. Iraq was by far and away the best place to start the liberation, for geographical, strategic and historical reasons.
2. A Moral Constraint on the "Debate." There has never been a plausible moral argument against the liberation. This is for obvious reasons. It is impossible to refute the claim that it is permissible to liberate 25 million people from a mass-murdering tyrant whose heirs were psychopathic sadists. You'd have to show that the invasion would kill as many or more than the tyrannical regime would kill given another 30 years' reign.
It is impossible to refute the claim that a mass-murdering tyrant with a WMD program, who has liassons with terrorists and shares with them the same enmity towards us, and who therefore could help those terrorists put WMD in an American city, should not be violently deposed by us.
3. Miscellany.There have been plausible arguments from prudence that liberating Iraq was too much against American self-interest to count as prudent. But I don't think those arguments succeeded, and anyway they are beside the point. Those arguments are for military strategists to evaluate; I'm not qualified. They are not philosophical or moral topics.
By the way, I was once scolded by a anonymous journal referee for using the term "self-interest." He considered it obfuscating jargon, preferring I say "interest." But that's not right. I have self-interests and non-instrumental interests in others' welfare. Both are interests. An argument from prudence against an action that will help others attempts to show that the sacrifice to the agent is too great. It attempts to show that, though morally permissible (and supererogatory, or "above and beyond the call of duty") the action is too great a sacrifice to be considered rational.