I have always held the opinion that the term African-American could only be used properly when referring to someone who was formerly an African citizen who has moved to America and become an American citizen. If they wish to retain their self-identity as both an African and an American, that's fine with me, as long as their loyalty now is purely to America in case of a conflict of interest.
Simply having dark skin or African racial characteristics does not make one an African-American IMHO.
If they were from Africa and immigrate to the U.S. they would have said the following....
I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty of whom or which I have heretofore been a subject or citizen<\em>
In that regard, there is no acceptable use of the term "African-American"