This was trash of them, but it's also out of context and forcing our way of seeing history on people who don't see it the same way.
Race wasn't a thing then so when people say Africans were selling their brothers they're basically trying to make it seem like black people we're savages with no loyalty, but like this says Africans we're selling prisoners and disgraced members of their family.
the problem is people try to rewrite history to make the Africans look like evil backstabbers, but in reality this is how the world worked. A perfect example is Australia's existence and the Irish slaves people love to bring up all the time. White people brought them there.
The problem with the Trans Atlantic slave trade is white people created race and made it so black people were inherently slaves. Africans didn't know they we're selling their race into slavery because to them and the rest of the world there was no such thing as black and white or race in general, just humans.
That's why when white people stepped on the Americas Native Americans didn't have problems making a Marvel team up with them to snatch the Aztecs and Incas. The biggest factory is White people we're just the most sinister group by creating the label of white people because before then a Greek or a Roman would be disgusted by the idea.