If you, a representative and believer in God, find yourself to be a "slave" there is an expected way you are to behave at that time and in that culture.Well, it's pretty straightforward the way I read it:
Slaves, submit yourselves to your masters with all respect, not only to the good and gentle but also to the cruel.
It's only in recent history that a large portion of the world (In Africa their still trying to sell each other) sees slavery as some great evil.
This is always the annoying part of this conversation. People always impose their current moral feelings on the past. As they look down their nose thinking themselves so progressive and superior, all while we live in a world that's confused about genitals.
We are no better than they are.