No one here is celebrating belief in white supremacy. Quite the contrary.
In the 19th Century, belief in white supremacy was not a point about which the North and the South disagreed. Most whites everywhere assumed white supremacy.
In the 20th Century, the North and the South diverged on white supremacy; the North got that particular point right sooner than the South did.
Recent elections show that, in the 21st Century, the North and the South are again reaching agreement on this issue, and they are both getting it right this time. That is what I am celebrating and, I trust, what we all are celebrating.