Dean just listens as he walks, fully intending on leaving Sam without acknowledging him beyond what he has done already. It isn't worth it - engaging in conversation, trying to act like they can get back to a place where they are brothers, again. It's better to treat him like a stranger. Then they can both move on with their lives.

But just before they make it outside, Dean turns around to look at Sam - ignoring that dismissive Bye, Dean.

"You're judging me?"

He huffs out a humorless, breathy laugh.

"For doing what I gotta do to survive in a world that you ended." He points at Sam with the pistol, emphasizing that you.

"Hate to break it to you, Sammy," Dean adds, and there is no affection in his use of the nickname, "But you don't got a moral foot to stand on."