That's because the VAST number of legacy admissions are decidedly white. You speak as if college admissions don't have its own built-in affirmative action for whites.
80% of all black judges in the US, 70 percent of all black dentists and doctors, 50 percent of black engineers and public school teachers, and 35 percent of black lawyers all graduated from HBCU's.
Some of the brightest and best Black CEO's of Fortune 500 companies, and black multi-millionaire / billionaire entrepreneurs graduated from HBCU's.
Point is, unlike what you suggest, it was never a question of capability nor intelligence. It was about admission.
Your arguments about AA aren't solely based on an article. You don't support the program .. period. Based on that obvious truth, it's more than a bit curious why you talk about black students while ignoring / making excuses for the biggest beneficiaries of the program .. and it isn't just white women who benefit most from the program .. so do white men or anyone else married to the women who benefit.
Your constant moaning about black students damages your credibility on this issue.