I think that this covers it pretty well:
“When admission preference is associated with skin color, the result is the strengthening of the ignorant stereotype that people having skins of that color are intellectually weak. This a canard, but it is reinforced by preference,” Cohen told The Fix. “Preference in admission is a very bad thing for the minority preferred! It is also morally wrong, because it violates the fundamental principle that the races must be treated equally in a decent society.”