That's not exactly true...
Fellow Africans willing to sell one another, Arab slave traders, and by the way, wasn't the first person to change indentured servitude to slavery in the Colonial America, black?
You beat me to it!
Ishmaelites have been in the business of slave-trading all the way back to the story of the Patriarch Joseph. In Genesis.
Other cultures moving here from Mexico, eastern European countries, Arab nations, China, et al, don't share white guilt in what our ancestors may have done. These people come from countries where people are truly oppressed. They never owned a slave and never shot an Indian and they could care less about ancient history.
This is partly what's happening in LA, viz. Mexicans are tired of blacks incessant whining w/constant hand out for freebies. Interesting times we live in.
The complete truth is that the tribes in Africa enslaved other tribes, some for tribal use and some for sale to other Africans, Arabs and Europeans. (This was similar to what prevailed in Europe during the first millennium). And the term Africa was simply the Roman name for that geographical land mass south of the Mediterranean. It did not connote any kind of familial, cultural or linguistic relationship between the tribes. Slavery wasn't some kind of exceptional practice. It was one of the benefits of winning wars, in addition to getting agricultural or grazing land, nubile women and useful implements, in a world that, until the 20th century, was ~90+% employed in near-subsistence* agriculture.
* Meaning one bad harvest meant hunger or even famine.