ld labors under the misconception that "vast majority" of Harvard students are white, and that therefore legacy admissions are still almost always white.
Affirmative action existed 30-40 years ago.
More even a generation before that. It is an inherent property of legacy admissions that they tilt the composition of the student body towards what it used to be, and away from what it would otherwise be today.
But racial preferences tilt the composition even more. Without racial preferences, but with legacy and athletics, 2% of those admitted to Harvard would be black (1% on purely academic criteria) as opposed to 11% with racial preferences.
It is a logical consequence of these two facts that, in the context of the US today, legacy admissions have a significant effect of making universities more "white" than they would be without them, and that, all else equal, the proportion of people who got in due to the legacy admissions policy is much lower among black students than among white students.
And racial preferences make universities less white and Asian and more black and hispanic than they would be under race-neutral policies.
It's not a straw man to correct ld when he makes false claims.