Right. And I wasn't even thinking of the "lying about getting Sam out of Hell" thing, I was thinking of the "breaking Sam's wall" thing. It's true, Castiel thought he could fix it, but that turned out to not be true (or while he had the ability, he was too high on power and rightousness to actually fulfill the promise). But even if he hadn't promised to fix him, hurting Sam really is the last thing you ever do in a friendship with Dean.