1) White on Black crime is not as prevalent as white on white, or black on black, or especially black on white. The reason? Virtually every time a white on black crime happens, there are harsher penalties levied because of bogus hate crime charges. White guy mugs a black person? Hate crime. White guy rapes a black woman? Hate crime. Black guy rapes a white woman? Rape. Black guy mugs a white person? Mugging.
2) It isn't law enforcement suffering from a pro black bias. It`s law enforcement scared to justly charge criminals. If a white guy beats the poo out of a black guy for, say, mouthing off to him. That`s assault and battery. If the black guy claims it was racially motivated though, the white guy will have hate crime charges added, automatically. If the roles were reversed, it would be much harder to add that charge.