It might not be such a bad idea …
... if the puppet government in Iraq promises an amnesty to anyone who lays down their arms and promises not to fight against the so-called government. If that government is going to have a lifespan of more than 15 minutes past the point where the American Imperium loses interest and wanders away to play with some other shiny little bauble, it's important to make it look like you're an actual government instead of being just a sockpuppet.
And, to give the people in charge of the Evil Party some credit, it's good to not immediately say "No, we will not permit Iraq to do this" when the news gets out that "anyone" includes the rebels who have been enthusiastically killing off American soldiers. Iraq is, at least in the speeches Maximum Leader Genius has been giving, an independent country that can set its own laws.
But it's doesn't seem like it's such a great idea for Evil Party senators to fall over themselves trying to support this plan. It might be good policy, but we are still at war there and American soldiers are still being killed.
I guess the Democrats got out of the door first with the "Oh, this is a SUCKY HORRIBLE PLAN and we CANNOT ALLOW IT!" speeches, so the Evil Party had to take the opposite position, never mind that it's 180 degrees from their traditional "Neca eos omnes. Deus suos agnoset" platform (to say nothing of the long-running conservative hissy fit about The! Nerve! of normalising relationships with Vietnam after they had the temerity to defeat us in a war.)
About the only way it makes sense is if you assume that the Evil Party has been a little bit too enthusiastically wapping each other over their heads with the STUPID STICK (™ talk.bizarre), since, as they've been cheerfully saying for the past quarter century, the Evil Party isn't the party of appeasement, and saying "great! go ahead! no problem!" is walking kind of close to, um, appeasement.