I am aware this is somewhat off thread, but it wasn't only Britain,and USA who were involved in the slave trade, it has existed for thousands of years, as most know, but the Barbary Pirates, from places like Morocco and Tunis, reportedly captured over a million and a quarter Europeans, over a period of some 300 years. There is a mention in the Diary of Samuel Pepys about it, a raid on the coastal village of Baltimore, Ireland, where pirates left with the entire populace of the settlement
The point being that many go on about the enslavement of black people, as despicable as that is, but either don't know about this, or choose to ignore it.