But Bobby's death? Bobby's death had one single purpose, as far as I can tell: to destroy Dean and thereby Sam. All the stuff that's messed up between them in seasons 8-10 is basically because Bobby's not there to call them on their behavior, to remind them what really matters, to serve as a sounding board for their more desperate ideas, to provide some kind of emotional stablity. It's perhaps telling that while Gamble killed Bobby, Carver's brought him back somehow in every single season. (Why don't all the people who've flipped out over Charlie's death consider that a little? Also that Carver's the one who turned Charlie into a recurring character instead of a one-off guest?)
It is also the only episode I can remember feeling indignant about while watching, because it's so blatantly manipulative. Sure, "Bloodlines" is trying to sell you a cast of characters for a show that (thank goodness) didn't happen, but it's pretty cheap stuff in comparison. Killing Bobby, and killing him this way, dragging the audience through it, is like smashing family heirlooms for fuel because you didn't lay enough wood away for the winter. This didn't have to happen. Seriously, how would the whole Leviathan arc have gone differently with Bobby still alive? The only arc his death enabled, as I said before, is the utter emtional destruction of Dean and Sam. (Also, his backstory wasn't bad enough? In addition to making him kill his demon-possessed wife and have a hinted-at bad childhood, they had to take it that extra step further? (And you couldn't find a better kid actor for Dean? Seriously?)) People joke about the beginning of season 8 feeling like a soap opera--well, this is what sent things in that direction.
But of course, no one ever talks about this. They just blame Carver for destroying the show, instead of praising him for salvaging it and dealing with the repercussions of such a damaging death in a realistic but slowly positive manner. *is a bitter Carver fan*