Some good points have been made here, but I'd like to add an observation or two:
Affirmative action is no different from reparations payments, it just takes a less-direct approch. Whites of today are penalized, economically, for actions of their ancestors -- and not even DIRECT ancestors -- just racially similar ancestors. And blacks today are given a bonus, and not just the ones who are descended directly from slaves, but ALL BLACK PEOPLE, even ones who came over from Africa yesterday. So, crazy as all that is, I think it shows that people use race as the marker, probably rightly so. It's just that only whites get screwed on it, nobody else.
Other things mentioned besides slavery: the Holocaust, and Japanese internment. All three of these things have something in common: Mixing racial nations with political nations. Blacks, Jews, Japanese and whites are all RACIAL NATIONS. Some African countries, Israel, Japan and the U.S. are all POLITICAL NATIONS. But see how confusing the two creates problems? If Jews hadn't launched a communist attack on Germany from inside its borders, they would not have faced Hitler's wrath. If whites had not enslaved blacks and brought them to the U.S., there would have been no slavery and subsequent problems. If the U.S. had kept out non-white immigrants from Japan, same thing - no problem.
Racial separatism gets a bad rap, but see how, if Germany had excluded Jews to begin with, if white slavers had left blacks alone in Africa, etc., these problems would not have arisen in the first place. That is not to say that you would not have wars over land between countries, but at least the wars would be honest struggles, unlike what we have today. Today, Jews in the U.S. make the U.S. its proxy fighter in the middle east --- that is bad because it is warfare based on deception.
Just some things to think about.