Wait til you find out Dick Cheney endorsed Harris! Probably the chief architect of the "GWOT", responsible for over 1 million dead. Fuck David Duke, but he's fuckin small potatoes compared to Dick-Vader.
If you're saying that earning an endorsement from antisemites for going against Israel makes Stein an antisemite, by extension, for going against Israel, because that is why Duke endorsed her, then yeah that kinda is what you're saying...
He just said he supports her. That's not an association. He agrees with her on her policy towards Israel. Unless you think her policy towards Israel is unreasonable and only would be held by a white supremacist, then its a ridiculous position to try and maintain, because it basically says that anyone who opposes us support of Israel agrees with David Duke and thus is "associated" with him.