This is closely related to established economic arguments about discrimination.

If *consumers* have actual preferences about the employees and employment conditions of the firms with which they do business– white customers don’t want to be served by black waiters, or actively prefer firms that they know have separate bathrooms for white and black employees, or whatever– then the market doesn’t tend to undermine discrimination. And when a prejudice is sufficiently widespread that members of group A can derive a sense of well-being and superiority from their membership in that group– which is to say from not being members of group B– then they have a strong reason to have such preferences. The so-called “psychic wages of whiteness” in the Jim Crow era south meant that white consumers derived utility from the enforcement of a strong wall of segregation– utility that offset the added monetary costs they had to incur. And free-riding was kept to a minimum, because the preference applies in each case (the racist white customer really doesn’t want to be served by a black employee), so the individual and collective incentives were mutually-reinforcing.