A lot of the "real Americans" in flyover country who rail about "coastal elites" do not like jewish people. It's fucked up and deplorable, but it's fact. Here you have Yarvin, who is a jewish dude who grew up between 2 coastal liberal environments (SF and NYC). He's trying to pander to the people who count on those "real americans" for votes.
EDIT: History has shown us that it often doesn't end well for these types of people. "Oh I'm one of the good ones, they won't come after me" usually lasts until the last of the low-hanging fruit is picked. Again, a modern tech-bro Clayton Bigsby. (Chapelle's show reference for those who don't know)
A good indicator can usually be their last name, especially if they are of German origin.
> wear religious garb that would make them stand out
Ever been to Brooklyn? How about Miami Beach? I'm from close to one of those places, and live in the other - and see Jewish people choosing to dress in religious garb every day. The more religious one gets (goes for Islam too), the more obvious it is to a passerby.