You know, it's probably because I'm inferring that - he's still in self-denial mode, which, if you look at Dean means drinking and snark (the "truth" thing at Sam about girls) and revisiting his decisions and being sure he did the "right" thing - when he knows, deep down, it wasn't at all the right thing. His insistence that he'd do it again is the problem, and he can't see that yet. Self-denial. But he's drinking heavier than we've seen him since, what was that, S5? And I think that's indicative of how much he's avoiding looking at the truth (and it's a major part of a Dean downward spiral, drinking waaaaaaaaaay too much).