|I hate this show for making me so crazy. But I can't help but to love it. This episode was fantastic! I felt Cas' pain. Why can't Dean and Sam just try to understand what Castiel is doing is for them? I don't want Cas to die especially by Dean's hands....|
In truth Cas hasn't really done anything neither Sam or Dean haven't done (making deals with demon and lying about it).
I think in Dean's case it's all too familaur and he doesn't want to go down the same road and make the same mistakes he feels he made with Sam.
In Sam's case he's probably seeing a lot of himself in Cas right now and not liking what he seeing.
In Bobby's case he's had a front row seat to both Sam and Dean's past mistakes and he, likely, doesn't want to see it all played out all over again.
In a way Cas is more a Winchester now than anything becasue he's done all the things we've seen not only Sam and Dean but also John do, just hopefully he can pull out this spiral before he crashes and burns.