Is there some kind of superpower that you think HR people have where they can look at someone and see exactly what dollar value they will add to your company?
No superpower. Just the interview process, which is the best tool available to evaluate a potential employee -- even better then *gasp* skin color.
Diversity can lead to a more productive work place or a great idea that you might not have had access to otherwise.
I see this concept parroted repeatedly in discussions like these with nary a real-life metric to back it up. How, pray tell, does having people with different colored skin lead to a "more productive work place"?