With reference to this, well, what he said.
But on the specific issue of: IF WE LEAVE IRAQ WE'LL EMBOLDEN TEH TERRORISTS!
Well, at the moment, we've pretty thoroughly convinced the terrorists that we're absolute morons. So the question should be, will de-enstupiding ourselves embolden the terrorists?
Maybe. Honestly, though, they seem pretty fucking emboldened already, if you wanna know the truth.