America is becoming an increasingly multiracial and multiethnic society. That can be a source of great strength, but it can also be a source of division if people know that they aren't all being held to the same standards. The only way to enforce the antidiscrimination laws in our multiracial, multiethnic society is by playing no favorites.
(For an empirical study of affirmative action around the world and the effects it has had, see Thomas Sowell's Affirmative Action Around the World : An Empirical Study.