"What part of 'shut up' did you miss?" Dean asks, still looking down at Sam's arm as he finishes bandaging it. He lets go of Sam's arm and then looks at his face. There's nothing he can do about his eye - no way to acquire ice - so he'll just have to rest that one out.

"We've got work to do, remember? If you're dead, it's gonna be a hell of a lot harder for me to kill Lucifer."

Ergo: "They were wrong to kill you. They were morons. The first question they should've asked themselves when they found out who you are is, How can we use that? They're freaking hunters, not civilians." They should have thought like hunters, should have realized that Sam could be useful, instead of just jumping the gun to kill him. It was stupidity.

But most of all, they just plain shouldn't have killed Sam. End of story.

Dean puts the first aid supplies back in the sack.