"It's interesting that Cas would give him this kind of barb-disguised-as-support, because it seems like a very Dean thing to do, and Dean is Castiel's model for how to treat Sam. So naturally he's going to be all "you're too important to lose even though you're a giant fuck-up." I just wish I knew the writers were doing this intentionally, and not because they really think Sam is a giant fuck-up."

Me too, cos it would stop me being utterly livid if that is why they had that line. If that really is what they think of Sam I reckon I've had it with this show.