What technological improvement helped slavery in the 16th century? In the 15th century, Admiral Zheng He of China led a massive armada to Africa, and came back with giraffes. Not slaves. Indian traders conducted trade with east Africa for centuries, without buying slaves. So did the Persian Empire.

Slavery is worse than other forms of discrimination. Separating children from their mothers is worse than discrimination. Or do you think all crimes are equally bad? For example, is a pickpocket as bad as a murderer? Or can we agree that murder is worse than petty stealing?