There are racists on both sides of the political spectrum. I'm not giving either side a free pass. It is what it is. So, don't flame me for what I'm about to say:
The man guiding many of David Duke's talking points for many years is a guy named John Tanton. Tanton is a multi-millionaire into eugenics.
At one point, Steve Bannon was so involved in eugenics that he wanted to make a documentary about it and give Mel Gibson the lead spot.
Both Steve Bannon and David Duke subscribe to the same racial and political philosophies. Trump is cozy with Bannon and knowingly spouts political rhetoric that is cooked up in John Tanton's non-profit organizations. And, when Trump ran for office, he denied knowing who David Duke was while Duke and Trump were well acquainted, as you pointed out. In addition, Duke was sending out letters to his supporters during the election, teaching them how to become electors that could support Trump.
Personally, I would feel more comfortable if Trump would simply admit the obvious. I hate to see his supporters groveling at the feet of the powers that be, claiming they have nothing in common with white supremacists (sic) and then relying on Tanton's talking points, research, and alleged facts about certain political issues. It's almost as silly as people telling me Obama was not a Muslim.
Gee whiz, people. Get the facts.