@Lash,
Sooo..... I'll just go with your premise, for the moment. Not that I agree, but it's not even the point here.
I must say I don't see the contradiction... In my opinion, you can perfectly base your decision in reality, and still have an idealistic perspective. I think that has only partly to do with the result.... (you can have a realistic perspective, and still be wrong in the end)
I think the realistic vs. idealistic thing primarily is a question of your perspective
beforehand, though. For example, you can say "we have to invade, and we'll work towards democracy after we've toppled Saddam - but there's no way of telling how long it'll take" - that's not only basing your decision in reality, but also acknowledging the imponderabilities of the future. A realistic outlook.
And there were many people around - at the time - who said that much. All of that was dismissed by the administration. Brushed aside in favour of an idealistic portrayal of the post-war situation.
That's what I'm talking about. The perspective
at the time.