No, I am very well aware of that. But they’re not saying “You can’t wear a BLM button because we do not think black lives matter, but you can wear a proud boys one if you want.”
They may or may not have that right - that’s going to depend on both the currently existing corporate rules and any state/local legislation.
I was thinking in particular about a case in the past 5 or so years where a company was sued for forbidding one employee from wearing a hijab while allowing others to wear crosses. It was a case of religious discrimination.
My point is that for this to be non-discriminatory it has to be a policy that’s handled in an even handed fashion. Of course it has nothing to do with the constitution - I’m not even sure why you’d introduce that unless you’re staying to strawman. But I know that I can’t fire someone for saying in the workplace that they agree with Trump unless I have a wholesale policy banning talking about politics. I’d be in trouble if I said people could talk about politics, but they could only say nice things about Biden and bad things about Trump. You might be able to get away with that at a locally owned auto body shop, but not at a major corporation.
My further point is that saying that black lives matter isn’t political, unless there’s a major political party that thinks black lives don’t matter. Rainbows aren’t political, unless there’s a major political party that thinks the LGBT community shouldn’t be visible. Books on gay parents aren’t political unless there’s a political party that thinks gay people shouldn’t be allowed to be parents. But that same party would allow a flag pin, or a yellow ribbon, or a book about a hetero couple with a kid. It’s only political when they disagree with it. Otherwise it’s just “normal.”