On one hand I can see the point of the South. We see in Exodus that there are certain laws that apply to Jewish slaves.  Later on in Deuteronomy we find other kinds of laws that apply to gentile slaves. As for Jewish slaves, they must be let go after 6 years. Gentile slaves are not to be let go of, but they can be if their master wants to set them free. But some of the most interesting points are made later in the books of Solomon. אי ארץ כשעבד ימלוך "Woe to the land when a slave rules."