I've seen the drama of no evil PCs allowed before. The DM ended up telling the player that his character could feel the stain on his soul as he contemplated the alignment changing act and basically offered the choice of "change your mind and keep your character or do it and he's now an NPC." The player was entirely too graphic in his description of the intended torture of the prisoner. TMI, guy, TMI. I wonder if he was drawing on his military experience in that, but more likely he had some baggage the rest of the group didn't know about.