They are saying that only black people are so ____ that they will intentionally avoid a black business and instead go to a white business. They are suggesting that the whites are the 'natural enemy' of the blacks. They are suggesting that blacks are inherently race traitors. Presumably, blacks are supposed to read this at some point and feel so guilty that they attend this restaurant, rather than be the race traitors that this restaurant explains to them that they naturally are. In a sense, they are trying to use guilt to strip their fellow blacks of their cultural heritage, and then cop those ends.