Dear People freaking out about Crowley stealing sam’s line. Calm down! Crowley calls Dean a jerk and Dean responds almost on instinct with Bitch, because of what’s said, not because of who’s saying it.
Crowley probably didn’t realise and he doesn’t look to me like he’s in a joking mood, the comment wasn’t meant as banter. Dean is the one that turns it, the way he says it makes it obvious he doesn’t care if crowley’s annoyed, he’s there to have a good time and noone is going to stand in his way. Demon Dean doesn’t take orders he does what he wants and If you try and tell him otherwise he will laugh in your face because what are you going to do to stop him?
Also the fact that we relate this quote to the brother’s makes it obvious how much dean has changed, not feeling sentimental towards Sam, he doesn’t care.

So yeah it’s more about Deans character than Crowley. Crowley isn’t pretending to be Sam, it’s just showing us that Dean is still Dean deep down behind the black eyes.