I think legacy status is a bit ridiculous, but legacy status admissions benefit those with higher socio-economic standings, not those of a certain race. The issue here is one of discrimination based solely on race. Legacy admissions are a weird from of classism (and therefor some degree of racism, I suppose), but not of race-based discrimination.
I think the difference is quite important.
It’s true that not every white applicant has a legacy status to benefit from. But if you look at the racial breakdown of students who benefit from legacy preferences, I think you’ll find far more white students than the in the overall student body.
And nowadays, legacy preferences -- I'm all for getting rid of them -- hurts the average white student more than the average black student, because they fill up the white quota.