The higher prices offered to blacks and females has been widely observed and the authors want to test the hypothesis that this is the result of animus on the part of the seller. Since the presumption of lack of animus of Blacks toward Blacks is never tested, there is little reason to agree with the author's conclusion that the prevailing discrimination is not due to animus between seller and buyer but rather to another plausible reason, namely statistical discrimination.
Discrimination can be along economic and social lines rather than race.
Blacks who have been economically successful may not identify with other less successful Blacks. Black owners may believe that if they can make it, so can others, and thus lower economic class blacks deserve no sympathy and in fact may deserve some antipathy. So rather than give a brother a break, the black owned dealership may charge the same higher prices to black buyers as do white owners. The same economic class animus might also apply to lower average income women. It would be possible to do a follow-up interview with black dealers and salespeople to determine whether they had any animus or sympathy to black buyers or were neutral as Ayres and Siegelman assume.