By locating these problems exclusively in the past, we can give ourselves a pass. But the reality is that these divisions and exclusions persist today. I don't know that anyone is suggesting that you assume guilt for something you didn't do. It's about assuming responsibility for how things are today. Inequalities persist not because, as one person below suggested, white people or culture is superior. It's that white people still hold all the levers of power (as do men, by the way) and so they self-interestedly (and blindly) buy into the notion that this is the world as it should be,  that meritocracy explains it all, and that it's sheer coincidence that discrimination on the basis of skin colour, religion, ethnicity, gender, etc was once legal and absolutely fundamental to our social ordering and national enterprise.