I think he assume you read the comment he put in his comment when you where commenting. Which is pretty short and this is it:
"They paid the moral debt with interest when they forced Africa to stop enslaving their own people to sell them.
Anyone who doesn’t know this is unqualified to speak about it or is being dishonest."
I do get your point which was europe had stopped doing slavery themselves (tacitly given peasants, indentured servitude, wager slavery [which under globalism increased greatly]) but were fine buying them as a commodity and then just deciding they can commoditization the whole race given how different they looked (one reason natives were not enslaved on that scale). Thing with commoditization slavery is it really treated slaves like a commodity and was more brutal than the type of slavery taking place in africa and more seen in history. For anyone or anyone I am in no way condoing or endorsing slavery but it is a complicated historical subject but I would rather have been a slave in many cultures than the typical american colony one or a typical dark ages peasant.