They can debate their separate philosophies to the death, but it won't change Dean's mind. A guy might be infected? Better to take him out before he rips out of his restraints and tears open someone's throat. Dean's seen it happen. A looter is camping in an abandoned building? Better to shoot first and ask questions later or you'll wind up shot over the territory. It happened to Dean — twice. He still has the scars from the shitty doctoring job he did on those wounds.

Get contaminated? Dying is better than risking being part of all of this. Dead would have taken death easily — doesn't regret that he was about to pull the trigger, even though he's survived so far.

"It's none of your god damn business what I do with it, so hand it over."

Dean reaches out an arm.

Sam's right, though, in that Dean has little faith in the rest of his men. He doubts they'll pull off finding the Colt without him. It needs to be Dean — but Dean would rather be dead with a bullet in his brain than a Croat, no matter the consequences.