The Hell is he talking about, denying him something? If they're perfectly happy together, then why does Castiel need someone else? Dean doesn't like to come off as a jealous guy, because he isn't, and thinking that there's someone else who can provide for Cas whatever he can't is a little irritating.

"No longer necessary? I'm the one here that's always at the bottom of the damn food chain, Cas. But hey - I get it."

Pulling a race card, Cas? Not cool.

"I'm not good enough for an angel, am I? At the end of the day, I'm just another meatsuit. A broken one, too, 'cause I'm a handsome bastard with a coupla parts missing, huh?"

Dean's always felt as though he didn't really deserve Castiel. For fuck's sake, why would anyone that holy want to be with him? He doesn't even know what he does in Hell, and he's sure that whatever it is doesn't warrant a Get Out of Jail Free card.