The Anchoress has a fine post about Iraq 1991 v. Iraq 2008, and asks a pertinent question at the end: "The question of why it was wrong to abandon the Iraqis to chaos in 1991 but is right to do it in 2008 is a really good one that I wish someone in the mainstream media with access to Mrs. Clinton, Mr. Obama, Mrs. Pelosi — or for that matter with access to someone like the anti-war George Clooney — would finally ask. I would love to hear the answer."
The answer is all too simple. In 1991, bugging out was right; it only became wrong years later, in hindsight. It's right in 2008 because of lack of foresight. Should we "do the right thing" now, the Left will be busily denouncing that decision as wrong come about 2025 - but then as now, only well after other people took considerable risk and trouble to correct the mistake, at a terrible cost.
Given the genuine cost of war, one hopes that those fighting it won't give up because of the wholly imaginary cost of being criticized for it.