If the sexes and races don’t differ at all, and if psychological interchangeability is true, then there’s no practical business case for diversity. On the other hand, if demographic diversity gives a company any competitive advantages, it must be because there are important sex differences and race differences in how human minds work and interact.You really can't have it both ways. Actually, there is very little "practical business case for diversity" except in Marketing and Public Relations.
There may well be "social peace advantages" to employee diversity as it helps forestall boycotts, lawsuits and other hassles. Claims of practical business reasons mostly represent attempts to make a business virtue of a social necessity.