Ignoring for a minute that you're the one that inexplicably brought post-modernism into the discussion (and even more inexplicably tie it to anti-empiricism)...

What empirically shows diversity is bad? Empirically speaking, certain groups are underrepresented in hard science. Empirically speaking, intelligence differences between those groups is somewhere between highly disputed and nonexistent. Therefore, a well-managed company would seek to exploit that arbitrage opportunity.

edit: Empirically, good working environments improve business results. Most decent people see the benefit in a diverse workforce in furthering that goal. And it would be beneficial if it just weeded out the types of personalities that are strongly averse to diversity.