I'm not following you.
I don't see how leaving Iraq now would be considered defeat? Where would be the humiliation?
It would be a failure to complete the objectives of giving the Iraqis an elected government, ensuring that the public wealth wouldn't be squandered any longer. (Some would argue that we could use some lessons on how to do this ourselves)
The biggest complaint is lack of security. I don't think our leaving Iraq would help much.