Many white people were literal slaves around the same time (in the 1800s and before). Look into the Barbary slave trade. Over 1 million white people were held as slaves in Africa. Even some Americans were held as slaves in the Barbary Coast.
“Sufferings in Africa” is a fascinating memoir of some white sailors shipwrecked and enslaved in Africa. The book inspired many white leaders in the US to empathize with the abolition movement.