Is the minimum wage racist?

Walter Williams thinks that it is:

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."