"You don't know a goddamn thing, Sam, except that pile of delusions you've got sitting in your skull," John spat back. He hadn't backed down, had barely even blinked, even at this change in Sam's expression, but he was already thoroughly sick of this little intervention. Turning away from his son as Castiel began to speak, John stopped.
Dean on the floor.
There was a moment there, a very dangerous moment, in which John nearly reached for the Colt to point it at Castiel instead, but that moment, barely even seconds long, passed as the details invaded the larger picture – the rise and fall of Dean's chest. Claire's anger, rather than hysteria – and logic prevailed.
It still filled John with anger, not at the action in an of itself, but the fact that it was one more protection of the creature in the trap. He wanted her dead, with every fiber of his being, and Castiel's words, Sam's further lunatic ravings, barely made a dent in that need for demon death.
"We're done here," he said, sharp, authoritative, before turning his gaze to Castiel there, nothing in the expression but stony resolve. "You, you do what you want with that thing, but you make sure this family never sees one bit of it again." Demon. Creature. Thing. It. For John, there was no identity there anymore, name or gender, and that would be how it remained. That – an identity beyond 'demon' – had been a privilege granted in a blind time for John after being giving a second chance at life, but it was being taken back now entirely, in every way. What was in that trap was every bit his enemy now as other demons before had been.
"And you're coming home," he said to Sam in that no-argument, I-don't-care-if-you-object tone that would accompany a deaf ear to any bitching, "willingly or kicking and screaming. Don't really give a damn which."
The declaration laid down, John moved to block exits that Sam might just now aim for, even as he calculated what he'd need to do to restrain Sam without resorting to excesses, weighing his own skills and arsenal against the potential of what powers Sam could now have. That he could even imagine his son turning those demonic abilities on a family member, let alone feel fairly sure of it, quietly broke John's heart without fanfare or outward sign of anything other than a soldier's determination in war.