It all comes down to the hiring pool. Compare the following two scenarios:
1. You're in a minority group (relative to the hiring pool), and your hiring decisions are skewed towards hiring other members of the same minority group (relative to the hiring pool)
2. You're in a majority group (relative to the hiring pool) and your hiring decisions are skewed towards hiring other members of the same majority group (relative to the hiring pool)
Why would the number of members of your group in the hiring pool change the morality of the situation? Take, for example, a business in a majority black neighborhood preferentially hiring white people. Seems bad. I think I prefer the "historically marginalized" justification more, although I think that has its own problems.
1. You're in a minority group (relative to the hiring pool), and your hiring decisions are skewed towards hiring other members of the same minority group (relative to the hiring pool)
2. You're in a majority group (relative to the hiring pool) and your hiring decisions are skewed towards hiring other members of the same majority group (relative to the hiring pool)