V. D. Hanson does a nice job of dissecting the various and variously contradictory attitudes of the convention wisdom with this perceptive essay, which directly addresses several arguments I've heard recently from various members of the peanut gallery:

Apparently a new exegesis has arisen that goes something like the following: The United States was wrong to go to war to take out a monster who deserved to be taken out but nevertheless should stay to ensure stability in a country that it has no right to be in.