How he identifies or defines himself is HIS decision and HIS business - no one else's. But in general, the world sees him as a Black man, not this "biracial" business, so I don't think it is that crazy to call himself Black. And not all people of mixed race are conflicted or have issues - that's rather insulting to assume.
Get used to me. Black, confident, cocky; my name, not yours; my religion, not yours; my goals, my own; get used to me. -Muhammad Ali