I don't think the Carol/Morgan philosophy debate is fuzzy at all. Carol has proven that she is open to outsiders and additions to their group when people show that they are equally working towards survival. Additionally, the person must show a willingness to work towards what's best for the group. This means people who are willing to kill or abuse innocents have given up their right to live because they have crossed the line of self interests vs. group interests. Second chances are possible depending upon the intent and consequences related to the misstep. For example, look at Father Gabriel. He has made some unwise choices, decisions that were both self destructive and dangerous to others. However, he has never intentionally set out to murder or slaughter innocent people in the group. Carol has no use for him, but she is not actively wanting to kill him. He has been a liability, but not an opposing force or enemy that needs to be taken out.
Morgan's position is borderline pacifism in that he only wants to take violent/aggressive action in self defense and is refusing to use lethal means under any circumstances. This attitude was fine when he was by himself as his choices only affected him. However, in a group, letting a proven "enemy" (who is intent on killing or abusing you) live only allows them a second opportunity to come after you again or a future opportunity to do harm to someone else.
I don't really see a debate here when we are talking about zombie apocalypse survival ethics. Morgan can keep his "all life is precious" mentality if he wants to go back to being a nomadic loner. He's going to have to give up that view if he wants to live with a group in community.