Supernatural, Season 2

Dean:
For what? For him to Hulk out? Infect somebody else? No, thanks, can't take that chance. [Sam stops him from leaving.] Hey look, man, I'm not happy about this, okay? But it's a tough job and you know that.

Sam:
It's supposed to be tough, Dean! We're supposed to struggle with this, that's the whole point!

Dean:
What does that buy us?

Sam:
A clear conscience, for one.

Dean:
It's too late for that.

Sam:
What the hell has happened to you?

Dean:
What?

Sam:
You might kill an innocent man, and you don't even care! You don't act like yourself anymore, Dean. Hell, you know what? You're acting like one of those things out there.

Dean:
Mm-hmm. [He pushes Sam out of his way. He leaves the room, locking the door behind him.]