Sorry, but how isn't that policy an indication of white supremacy? Saying to people "Yes, we fought and won your freedom, but obviously its going to take us more than a hundred years before we actually start treating you as fully free".
Also with regard to Sanders, that is a valid point - but it (the failure to implement programmes because of GOP obstructionism) happens to everything and everyone that isn't something they have proposed; that is why the US is in the state that its in, why Merrick Garland isn't on the Supreme Court, why they are successfully undoing abortion rights, and why any sensible legislation over gun rights, campaign finance reform or anything that lobbyists don't like doesn't get passed.