Dean just stood there for a moment, watching what was going on. He wasn't slow on the uptake, but his time here had certainly been some of his stranger moments, which was saying something for a hunter.
He just shook his head slightly at Cas, but he didn't hide the hint of a smile; he did like the rebellious nature even if it didn't make any sense. The asshole in the door looked more like the bad and ugly than any good, and he sounded it too.
"Understand the attitude with the angel, but I suggest you take it down a few and show me Sam." Dean didn't pose; he didn't pull the gun. He stood there, more than ready to beat the everloving shit out of Carter wanna be or die trying all to get to his baby brother.