This is not a condemnation of Ron Paul, but of a small> segment of his supporters.
Specifically, Paul has become the “it girl” on the (literally) Neo-Nazis and White Nationalists. My guess is that his generally isolationist foreign policy appeals to him.
I have no doubt that Paul is horrified about this, and he needs to do something.
I’m not entirely sure what, maybe giving a speech at a synagogue and having pictures taken with a Yamulke on.