You are so wrong. There are magnificent black opera voices, both males and females. It has been a challenge to cast an African-descended person in a European opera set in Italy, France, etc. But I think most of today's audiences would just ignore the appearance and listen to the vocal quality.
Laudate Dominum de Mozart, sung by Barbara Hendricks
Pari Siamo from Verdi's Rigoletto, sung by Robert McFerrin (father of pop singer Bobby McFerrin)