“Then what is the point, Dean?” He’s half just responding with whatever comes out, and half genuinely asking, because for the life of him, he has no idea what the point of this, of any of this, even is. From what he’s seen, none of it makes any sense at all. It’s just stupid.
And, yeah, he wishes he’d kept his mouth shut a few seconds longer, because as soon as the words are out he knows what they’re going to do, he knows coming. He knows his brother, and he’s tensed and waiting for the inevitable snap. It’s sort of rare that they ever come to blows over things (him and Dean, that is - he and Dad get to that point almost every time they’re together; every time Dean doesn’t step between them, that is), but it’s not completely unheard of.
Knowing it’s coming doesn’t mean it doesn’t startle him a little, or send his breath out in a “Hnnph,” sound at the impact with the wall, because he doesn’t dodge out of the way before his brother’s on him. He shoves at Dean with one hand as soon as his instincts kick back in, before he’s even actually caught his breath or thought about it, getting ready to throw a punch with the other hand because he’s still pissed off, sort of itching for a proper fight right now, and just because he said something stupid didn’t mean he didn’t mean it, and all of this is just getting to be too much to deal with.