I think you're misunderstanding; this is a logical exercise. The best is a hypothetical ranking, and to add a independent variable which means we must detract from hiring the best person. To disagree would be to say someone is better strictly because of the color of their skin.
It's like if you were tasked with buying the most powerful engine produced for a locomotive. How you define powerful is arbitrary and is an optimization problem on its own, but if you then say "and the engine block must come from the factory painted red" you are, by definition, no longer optimizing for the fastest engine, you're optimizing for the fastest red engine. Being red is independent from being the best engine.
