( Sam does his best to bite back a sigh. ) If we were back in our world, I'd get the argument. But we're not; we're stuck here. And we have no idea what we're up against.

( Appealing to rationality is probably his best bet here since sentimentally won't work. As much as Sam's heart breaks for Jack in this situation, if Sam were in Castiel's shoes, he'd also be wary. But he's also not going to abandon Jack. )

You don't have to deal with him if you don't want. He'll probably want to keep an eye on me, but we can talk separately for now.