I am not sure how useful or not guilt is in shaping good policy. I do believe though that while slavery was terrible in itself, its impact was far worse than simply demeaning other human beings and treating them like property. Slavery goes hand in hand with racism. Many times in the West these two went hand in hand with the theft of knowledge and resources from the oppressed and taking credit for it. It also involved wiping the contribution of the oppressed out of the history books, which is why minorities have to struggle to reclaim knowledge of themselves to understand where they stand in the world. This doesn't just apply to the US by the way, it is all over the world. I know this cause I have seen it myself. Like I said before, guilt may not be useful in approaching any decision, let alone a political one. But do not underestimate the impact that slavery has had on American society. It may have happened centuries ago, your ancestors may or may not have been involved, it's not on your hands, but its impact (economically, socially culturally and otherwise) has pervaded every aspect of American society.