I'm pretty sure it is protected under the first amendment, especially as long as you don't actively advocate direct violence etc.

Not in the workplace it isn't. If you allow employees to openly use racial slurs and supremacist ideology in the office the courts will happily throw the book at you when someone files a discrimination complaint.

Will they throw the book at you or at the company?

"Pretty sure" is not gonna cut it here. White supremacy is nothing but a threat.

Ok, I'm absolutely sure that hate speech is protected under the first amendment.

> White supremacy is nothing but a threat

That's not what the supreme court seems to think.

> there is effectively no "hate speech" exception to the free speech rights protected by the First Amendment

https://en.wikipedia.org/wiki/Hate_speech_in_the_United_Stat...

Yes, but that does not mean al speech is permitted in the workplace. A company that permits employees to display neonazi posters will not last very long.

You can be an open racist or you can collect a paycheck but you can't do both.

White Supremacy isn’t a monolithic specifically defined thing. There are certainly kinds of white supremacism protected by the first amendment. For example, the ideas and works of Spengler.