I'm not sure his concerns about "emoldening" by leaving are necessarily valid. It's certainly conventional wisdom. But, it really depends on what the motivations of the insurgents are and the basis for their nontrivial popular support.
However, I think it's really time someone gets Scotty or George or Dick to answer this question:
Do you envision a time when there will be no US troop presence in Iraq?
Is it the goal of this administration to have a permanent troop presence in Iraq?
Who knows, maybe keeping 30,000 troops in Iraq permanently is even something I'd support, but it's unlikely that I or most Americans would support it at a cost of dozens of lives per month.