Since any theory of racial differences has been outlawed, the only possible explanation for black failure is white racism.
Since we are required to believe that the only explanation for non-white failure is white racism, every time a non-white is poor, commits a crime, goes on welfare, or takes drugs, white society stands accused of yet another act of racism.
The dogma of racial equality leaves no room for an explanation of black failure that is not, in some fashion, an indictment of white people.