A sub who can't take a little good-natured riling up isn't one that Sam could see himself with. So long as nobody said anything hurtful, at least.

He's pulled out of his thoughts by Balthazar and hums at the question. "Well. He's intelligent. Willful." He looks at Castiel and grins. "A bit of a brat, when he feels like it. Which isn't a bad thing at all. And he has beautiful eyes."