The Alt-Right's anti-semitism is autistic. Traditional/Orthodox Jews are some of the most reactionary, pro-free market and generally productive peoples out there. While true that they are over-represented in left groups, saying gas the Jews would mean killing a lot of innocents while leaving alive many actual parts of the cancer of progressivism. 

My favourite instance of this was when stormfront supported Corbyn because apparently Theresa May is Jewish/has ties to the Jewish world order, which even if true is still ridiculous because Theresa has a whole lot of reactionary world views and goes to show the usefulness of Jews. 

It's sad to see such an ally swept aside by a few autists and making Hebrews resentful, thus more likely to become part of the same red plague. The right is fractured as is.