Eh? Racism judges people by their race, and judges different races differently. The word fits just fine. Adding "differential" was unnecessary, but maybe added

Eh? Racism judges people by their race, and judges different races differently. The word fits just fine. Adding "differential" was unnecessary, but maybe added to highlight the uneven extent of the negative judgement. Having said that, the GP does not provide any evidence that racism was the motivating factor here.