What sets the “immigration policy” in a free market, is the private decisions of many different people who choose who to (and who not to) hire, purchase from, lease to, sell to, etc.
In a market setting, racists who arbitrarily discriminate are forced to pay for that decision. If an employer refuses to hire anyone of a particular race or sex, they are limiting their potential pool of labor. With self-imposed diminished options to choose from, the most productive employees may be excluded, and the firm overall will