because chattel slavery of people from sub-Saharan Africa existed in the western hemisphere for centuries and under several the rule of multiple nations, it is a most tangled history and word usage reflects that...

then there is both the polite and most impolite ways of referring to these people... and the logic is often quite twisted

an offshoot of this is how the term latino/latina is used... as a person who is half Italian it never made any sense that only those of hispanic extraction were meant... after all, where did the term latin come from the in the first place? but the roots of this go back to how the enslaved native peoples of the Americas had interbred with both the Spanish ruling class and African slaves - and their offspring where not considered to be pure enough to qualify as people of worth...

as for what is acceptable... no matter what term is decided upon, the racists out there will turn it into a derogatory one and taint it with their vileness