I think this is a revealing psychological tick. The Left has spent decades practicing the art of dismissing facts by attacking motives. Conservatives are biased by nature while liberals see the world clearly. Well, it turns out you can't make that kind of argument for so long without starting to believe it. The rule for the Left today is only to fight wars if your motives are indeed pure.
Purity is determined by unalloyed altruism and utopianism.
Indeed, just this morning I watched Bill Clinton justify sending troops to Kosovo because such a move was consonant with his new expansion of hate-crime laws to cover homosexuals. In short, the war in Kosovo is a war to end hate crimes. Well, that's very nice. But if that's the case, I'm painting a big peace sign on my van, buying a bong, and moving to Canada. Last week, en route to N'awlins, I hurriedly filed a piece with an unfortunate typo.