I agree with your account, the problem is how many perceive slavery. Here in the south (USA) many still think the slaves before the Civil War were "happy". They obviously weren't slaves. Until ALL mankind looks slavery fully in the eye for understanding, we will continue to undervalue those other then ourselves.
I don’t think there can be a bright line between acceptable and unacceptable coercion of liberties.
I remember story how Irish migrants were used to digg deep holes. Walls could collapse any moment, and bury the crew alive. Slaves were deemed too valuable to risk in such jobs!