It is easier to face the demons of others than a demon of your own. The Holocaust wasn't our demon. It doesn't really cost anyone in the US political capitol to explore the depravity of the Nazis. If we want to do the same for the confederacy (or any of the other dark corners of our history), we have to acknowledge that we are not superior, that such atrocities can happen here as well. There is a huge chunk of the US population that believes the US is god's anointed nation. Anything that distracts from that narrative must be sanitized.