If that’s the case, how far should they be allowed to go with a ban? What happens if they decide that fans of an opposing team shouldn’t be allowed to attend games? Or people who have been oppositional towards ownership or management, like the press. What about banning everyone who works for a vendor or partner because they are sour about a deal going bad or relationship ending? What about politicians or people with opposing views (I don’t believe that’s a protected class?).
Edit: updated to use examples that aren’t part of protected classes.
Half your examples would be flagrantly illegal. There's no comparing banning members of a rival company you don't like, and banning a race. These aren't even remotely similar from a legal point of view.
In many states you can legally discriminate against people based on politics. Not California however. Could be a very effective way to keep “that kind” out on both sides.
Yes, various states add more protected classes. Height and weight are protected classes in Michigan. I do wonder just how enforceable some of these are; if a bar in California bans somebody for wearing a nazi armband, I have a hard time imagining them losing a lawsuit about it.
Regardless, I don't think there's any state in which affiliation with an employer is a protected class. You can't compare this to race or sex, which are protected classes on the federal level, in every state.
Edit: updated to use examples that aren’t part of protected classes.