I've been playing a cannibal for a while now and the best advice I can give is to just make a side trait of your character and don't center your character around it. You don't even have to be a hostile cannibal in the traditional sense. I first started out hanging around on the coast and trying to convince people to kill themselves because the world has ended. ICly using the logic if I didn't kill them myself then I wasn't the bad guy. Don't be the cliche creepy guy it's been done a thousand times and most can figure out something is wrong ICly with you right away.