Why do you play with people who insist on abusing the weak and helpless who can't fight back? Seriously, what kinds of games do you play where the question of "but what if they beat their 5 year old daughter into a coma, go and get drunk, then kill the barmaid?" is a legit question?
Alfred has had his life put in danger by Bruce Wayne's crusade dozens of times just in the TV shows. He's been poisoned, shot, stabbed, and exploded on more than one occassion. And there has never been a moment of "well, this is too much, good-bye"
Sam followed Frodo across the flipping continent, fighting for his life on multiple occassions, had abuse heaped on him at the gates of Mordor, and still followed Frodo into metamorphical Hell. Sure, Frodo wasn't carving Sam up like a thanksgiving turkey most weeks, he was worthy of being loyal to, but the vast majority of Player character's I've seen are the exact same. They probably wouldn't even scream at and insult him like Frodo did towards the end.
Maybe play with people who aren't going to abuse and harm those weaker than them for giggles and the idea of loyal NPCs who won't betray them won't seem so far-fetched.