It is far too easy to hide discriminatory practices when subjective measures are used. Affirmative action was certainly needed to right the wrongs committed prior to the Civil Rights Era. Quotas, set-asides, and racial balance can only be justified in this context. In the wake of the Jim Crow Era, the American people did not have the patience to let racism die a slow death over several generations. Allowing subtle forms of racism to persist may have prolonged discriminatory practices indefinitely.
While there are still people that maintain bigoted ways of thinking, I think we have come to a point were affirmative action does more harm than good. However, the only way to know for sure would be to end affirmative action and to monitor the consequences. It is perhaps for this reason that the Supreme Court has chosen to err on the side of caution and allow some affirmative action policies to be maintained for at least the next 25 years. The blatant use of quotas has been struck down, but this hasnt protected corporations and institutions from lawsuits. Just as the prohibition of discrimination has resulted in more subtle forms of discrimination, the prohibition of quotas has resulted in more subtle forms of affirmative action. Quotas will not go away until racial imbalance cannot be used as evidence of discrimination.
The problem with quotas is that racial imbalance is not just the product of discrimination. There are other confounding variables aside from race. It has become apparent that socioeconomic status is a better predictor of academic aptitude. Although there are correlations between socioeconomic status and race, it is not right to perpetuate a system where performance is not rewarded. The initial effect of affirmative action was to challenge bigoted ways of thinking. Now that those deeply ingrained beliefs have been challenged and adjusted to reality, the persistence