Research showing a social issue isn't an issue doesn't get done much. And when it is done it's usually by outsiders. This is a case where the absence of data should not be used as a suggestion there is no data.It isn't a hate crime to refuse admittance of a potential student because their scores are lower than other applicants. I'd imagine that if only test scores and grades were used to admit students in the 1970s and 1980s, we'd see a much different ethnic distribution of students in US Colleges today. The whole point of Affirmative Action is to admit the thumb was on the scale 20 years ago and that thumb impacts applicants filing for admission today. It isn't about discriminate treatment of race, disregarding any care for qualifications.
To the best of my knowledge, affirmative action has led to no disparate professional outcomes in the fields it has been used.
Furthermore, we have what we saw in California. Remove AA and more blacks got degrees because they were more likely to graduate if they weren't in over their head.