Killing a POW, in a modern sense, is wrong in every example. In my military training, killing someone who has been captured was never an option(then again, I wasn't trained as an officer.) You've healed the guy, accepted his surrender, and in doing so made him your responsibility. He was resisting you, but not with his own body, he was trying to get his buddies to free him. When he became your POW, this was an assumed risk. That's why I was trained to keep them well behind the lines of combat and to separate the officers from the enlisted. So I'd say that it would be against the conscience of any LG character to kill a POW.