FWIW, a lot of American blacks have similar ancestry, except for the Arab part.
In the bad old days, 1/16 black ancestry made you black, unless you decided to "pass." At present, you are black if you have any black ancestry at all and you say you're black. Or if Ward Churchill can be an Indian just by saying so, then maybe you can be black just by saying so, as long as you spout the required leftist jargon.
As Cicero said, the implication in America (and elsewhere, especially in Europe) has always been that other races are an impurity to the white race (like how that some dirty water added to a bowl of clean water gives you a bowl of dirty water).