"What proportion (of x ethnic group) would you like?" is a question that greatly devalues the contributions of the individual student. Would you say, "You're a great interview candidate, but we already have a tall guy,"?
Discrimination happens when you treat equals as unequal, or unequals as equal. There is a world of difference between "we already have enough asian compsci majors", and "we already have enough compsci majors, but there is room for a sociologist".
Surely you're aware that this literally and explicitly happens in the context of college admissions. "We already have a couple tuba players, try Yale."
She had a sterling high school record, but they wrote a rejection letter explaining that they already had a woman attending the institution.
The punch line, as it were, as I recall it, was that "a woman" did not mean one undergraduate woman, but just one, period.
So, she went to a much less prestigious and well-known school, majored in math, and ended up being a programmer instead of an engineer.
I am not sure if she was bitter about it.