If you want to keep commoners calm, stop the slave talk. Like jaune stated in an earlier post, certain words cause people to go into a frenzy. Slave is one of them.
Adventurers understand noble arses exist in any realm; they take due note and avoid them. No adventurer signs up to become a slave.
Nobles, who are smart enough to understand that 'nobility' holds one to a higher standard of conduct, treat adventurers with due respect. "Due respect" for some nobles may indeed mean treating adventurers as dogs. Good realms and good nobles know better. These nobles reap the rewards of magical items, easy item repair and beast-free lands.
Rubbish in a historical context. Nobility was often some of the most depraved, callous and cruel figures we know of. Besides Magical items are fluff, some people like to have them, but really they do very little in game terms. And with the introduction of too much peace, realms are often LOOKING for monsters and undead to fight.
