What prevents farquars in no witchcraft for sale from seeing gideon as an intelligent and capable adult?

In no witchcraft, Farquhar's own the farm land. Gideon was their cook. The race was labeled as inferior, to which Gideon belonged and this prevented Farquars from the sale. The story shows the racism as a barrier in realizing the cultural values of the Black Africans by the "blind" white South Africans.