Yes? Companies do this all the time with codes of conduct and nobody really thinks twice about it.
Nobody would think it's bizarre that (hypothetically, I don't know what their actual rules are) Coca-Cola has a rule barring employees from wearing a "Pepsi > Coke" shirt to client meetings.
> where we try to legislate for things that are in many cases subjective?
We do this all the time, even in our actual legal system.
"Disturbing the Peace" is one example off the top of my head of something that's incredibly subjective that we consider the purview of the legal system.