I don't get the idea of "exile" or "feeding to zombies" as a punishment in a zombie apocalypse. "Oh no! The world is being overrun by zombies! Let's make even more!!!" Don't they have enough enemies already? The correct answer is: Forced labor for everyone. The single most precious resource in a zombie apocalypse is humans. Food might be hard to acquire though I wonder why no one ever even considers going to a farm but as long as people are capable of doing labor a camp of survivors should never get rid of them. Even that rapist/murderer has more value alive than dead (could be a test subject for a zombie vaccine or something, or to test if water or unknown plants/animals are safe to consume, something like that). Plus, the girls can be safely separated from the rapist under guise of punishment, while helping them overcome their trauma by keeping them busy, and also give them time to get to know other people in the group so they know who they can turn to if they need help.