I fully support equal opportunity, but Affirmative Action is nothing more than government-sanctioned discrimination. Affirmative Action acts to deprive one group today to "make up" for another group being deprived in the past. That is simply not right. Heck, international law even forbids collective punishment.
Over time, vigorous enforcement of equal opportunity would work. Unfortunately, we, as a society, are not patient enough to wait for the scales of equity to come back into balance. Instead, society puts the heavy thumb of affirmative action on one side of the scale to speed things along. The result is a statistically "equitable" result that is achieved through unfair means. This does not promote true equality, but cheapens the achievements of those who are unfairly advantaged and promotes resentment and hatred among those who are unfairly disadvantaged.
Of course, any discussion of equal opportunity or affirmative action is behind the times. Equal opportunity is blind to results and affirmative action is blind to anything but results. The currently favored term is diversity, which embodies the optimism of equal opportunity with the results-orientation, but not the negative connotations, of affirmative action.