On the slavery point, I would recommend broadening the perspective from just the recent history of white owners of black slaves to the greater history of slavery. For example, the example of ancient Rome and Greece. At least, if you're interested in a defense of slavery -as such- as opposed to just how Americans/Europeans did it.

Of course, Roman slavery still had plenty of problems but it's significantly easier to find examples of humane and (relatively) equitable treatment of slaves (who could be well-educated and own their own property) in Rome than in Europe/early America. And then there was the prostitution/torture/slave soldiers...