One of the more insidious effects of minimum wages is that it lowers the cost of racial discrimination; in fact, minimum-wage laws are one of the most effective tools in the arsenals of racists everywhere, as demonstrated by just a couple of examples. During South Africa's apartheid era, its racist unions were the major supporters of minimum wages for blacks. South Africa's Wage Board said, "The method would be to fix a minimum rate for an occupation or craft so high that no Native would likely be employed." In the U.S., in the aftermath of a strike by the Brotherhood of Locomotive Firemen, when the arbitration board decreed that blacks and whites were to be paid equal wages, the white unionists expressed their delight saying, "If this course of action is followed by the company and the incentive for employing the Negro thus removed, the strike will not have been in vain."
Tragically, minimum wages have the unquestioned support of good-hearted, well-meaning people with little understanding who become the useful idiots of charlatans, quacks and racists.
The Brotherhood of Locomotive Firemen example occured in 1909. The similarity between that and the South Africa example is that both took place in socieites in which racial discrimination in employment had not been outlawed. That makes them irrelevant to Williams' argument that minimum wage laws are racist today.