Im not sure this will ultimately be an effective argument. You cant favor people for being a certain race. But you can favor people for other reasons, which may result in more people of a certain race. That doesnt violate the Civil Rights Act. You dont have to meet racial quotas and in fact trying to do so will likely put you on the wrong side of the law (see the recent affirmative action case).
The argument seems to be that legacy admissions are wrong because they end up favoring white people which violates the Civil Rights Act. But it’s not actually discrimination by race. Any method of choosing will have imbalanced results, unless you do the one thing you CANT do and choose by race.
The article doesnt make any claims that legacy admissions are in and of itself illegal. Im just not sure what law legacy admissions break.
Also, a popular feeling that it’s unfair is irrelevant. Thats a job for congress.