This has been bothering me for a while.
He's not black, he is biracial. His mother is a white American, his father is a black Kenyan. Why does this make him black? He had a middle class white upbringing and, according to his own autobiography, he didn't attempt to explore his 'blackness' until he was in his late teens and afterwards. (seriously paraphrasing). He is married to a black woman, and probably involved in her family also. Great.
I've read articles about him in UK papers and they refer to him as biracial. Most papers around the world do.
So, why is he 'black'?