I agree with many of the others who said that this issue can't be addressed without taking both the roleplay IC and the OOC motivations and desires of your playerbase into account. This doesn't always make for the most realistic gameplay, but that isn't the goal: We are here to have fun and be entertained (while entertaining our fellow players at the same time). Also keep in mind that those that play (and enjoy) slaves and their masters can at the same time have several alts who are quite opposed to the issue IC. So I think a good compromise would be the best approach.
Now for what Xahu's spys would be able to gather from my Chars:
Lord Athian Hoggard - Doesn't mind slavery as a tool to redeem people, like criminals who get a chance to work their way back into society. Does not condone mistreatment of a slave, both physical and verbal. Would personally prefer slaves to be owned by the crown/authorities rather than individuals. They could then in turn allocate these men and women as it is needed, loaning them to people or institutions while keeping an eye on the behavior and well-being of the individual slave.
Killian - Nature has plenty examples of the weak performing services for the strong. There is little wrong with that, as long as the strong tend to and care for the weak that serve them. The truly strong, though, are those, that can let someone grow stronger at their side: While they will lose a slave at some point, they may well gain an ally.
Arondale - Doesn't mind slavery, but thinks that few people are fit to be good masters. In his opinion it isn't slavery itself that has people worried, but the tales of people mistreating their slaves.