Affirmative action & Discrimination?

What are the strongest arguments that a defender of affirmative action could use to rebut the reverse discrimination charge? How persuasive do you find these arguments? For instance, do you agree that even if affirmative action policies discriminate against some white men, the potential benefits from affirmative action far outweigh the potential costs? Do you think that this type of cost-benefit ysis is relevant to understanding the ethics of affirmative action?