Here’s the ‘anti-war’ explanation in a nutshell: the extreme left detests George W. Bush and the Republican party. Prosecuting a war is a huge example of the power wielded by the President.
The loony left is absolutely enraged that the president is successfully using our military in an aggressive fashion: never mind that they disagree with the threat posted by Islamofascists or whether or not Saddam was a threat to the US (Alan Greenspan this week explained at length that Saddam WAS, and why he needed to be taken out, to avoid catastrophe of the world economy).
The left is ENRAGED by the aggressive military moves Bush has made. The context, or greater ramifications of democratizing the Middle East doesn’t even enter into it. Their entire reason for existing is to thwart any move by Prez Bush, be it privatization of Social Security or naming an Att. Gen. or commanding the US military.
The hard left detests the fact GWB was elected, re-elected, has so much power and chooses to wield it. They seek to curtail his power. That’s the entire anti-war sitch explained in one sentence. And I completely believe it to be true.