Shalom Rav Shalom,
I don't remember where the passage is, but Rav Kook has a counterintuitive insight into slavery. He writes that since the slave is the property of the master, the master has an interest in taking care of him. He contrasts this with industrialists such as mine owners who pay "slave wages" and don't do anything to insure the safety of their workers. If and when they are killed in accidents he can always find more simple laborers who have no choice but to take the position. It does seem to me that his words were meant more as a critique of modern capitalism and the industrial revolution than as a defense of slavery, but they are certainly food for thought.
kol tuv,
Rav Zvi Leshem
