There's no such thing as 'pure African' (genetic diversity) and they aren't Black. They have had their own ethnic groups for millenia. Calling them Black is as disrespectful to them as us going to Ghana and declaring ourselves to be Igbo or Yoruba simply because we look like them.
Black people come from Africans, but are a unique ethnic group unto ourselves. Different history, culture, philosophy, heritage, language, etc.
Y'all rail against this but here goes.
Me, a Dominican, and an African are in a car and a KKKop rolls up on us.
Who gets to not be Black in that scenario?