"The Jews can just start their own companies" was an argument for firing them. It was wrong then and is still wrong when applied to othes groups.
People get fired for being hostile to coworkers all the time and this is no different.
To be clearer of my perspective: So if they are nice to their coworkers(jew, PoC, or whatever) but then after work goes and hangs out a sign that says "I hate Jews(or PoC, or whatever)" they should still be allowed to work the next day, assuming they continue to not let their personal beliefs interfere with work.
Clearly this person is a moron, and needs to change their personal beliefs, but that's a totally separate issue, unrelated to work.
Decent People refusing to employ anyone who thinks Jews, among others, are subhuman is NOT the same thing as Indecent People refusing to employ Jews.
Basis For Arguments Matter™
In Europe it's far more accepted that Nazism is more dangerous than simple 'beliefs' and that there are boundaries where speech ceases to become acceptable in society. See Karl Popper's Paradox of Tolerance. Try waving a Nazi flag in Germany and your feet won't touch the floor.
I'll refrain from discussing if it's a good position. The ACLU already laid out the pros and cons.
(b) Most people being called Nazis are not Nazis.
Rational Basis is a fairly easy standard to meet, but if your only rationale is "he's a Nazi" and he's not actually a Nazi, then you have no rational basis for discrimination.