Are you kidding? Antisemitism is a fundamental part of the alt-right.It's a fundamental part of the Left, much of the antisemitism you see on comment sections are leftist-trolls.
This article is from the UK, antisemitics there are leftists.
See: "left-wing antisemitism"
My son, just turned 18, considers himself Alt Right. I had to ask him what it was. Gamergate got him involved in politics. Apparently there are a huge number of millenial males who consider themselves alt right. One interesting characteristic I see is that they have no fear of being called racist. That card no longer works on the next generation. They post to sites like 4-chan, and do weird and funny trolling stuff, like convince women to stop wearing female products and be 'free bleeders' to protest male oppression or the patriarchy.
Amazing how many women on the internet actually fell for that and posted photos of themselves having what I would consider a very embarassing accident.
Their call their opposition 'sjws' or social justice warriors.