Naomi is, as usual, wrong. The David Duke/Trump issue primarily revolved around Trump's reaction to it: when asked to condemn the KKK, David Duke etc., he professed to not having known anything about David Duke, or the KKK, and refused to condemn the KKK even when given the option several times.
Claiming that "I don't know anything about David Duke, I don't believe I've ever met him" was particularly interesting, because he'd discussed David Duke in 1991, and 2000 a couple of times: "..., you’ve got David Duke just joined — a bigot, a racist, a problem. I mean, this is not exactly the people you want in your party." -- when discussing (and dismissing) possibly running for president then.
But when it came to 2016, he spent quite a while being evasive about Duke and the KKK, and then appeared to disavow them to succour the media: "Sure, I would do that, if it made you feel better."
In short, then, the issue with Trump and the KKK came about not really because the KKK supported Trump, but because he seemed to have so much difficulty in accepting that this was, perhaps, a bad thing.
That aside, then, turning to Corbyn. I have not seen how Corbyn has reacted to the association with David Duke. This is, perhaps, not surprising, since the story is an older one. It shouldn't surprise me, though, if Corbyn were equally naive and slow to disassociate himself from the ex-KKK leader. After all, he's doing about as well on anti-Semites in general; why should one more racist make a difference?