I can never understand people who complain about characters like this taking in slaves. Systematic slavery is a serious moral issue, but refusing to take part in that system does nothing for the people that are actively being victimized. Until he's presented with an actual choice that could weaken the system, he can only take them in himself or trust others to treat those people better than he would, and from what we've seen of this world that's an abysmally stupid thing to trust others to do.