I don't think hypotheticals are particularly relevant.
What I would argue is that (unless you're the bouncer at a nightclub) it is pretty shitty to refuse someone entry without explanation. If you don't know the reason, you should be willing to call your superior and find out, and maybe sort out the situation properly.
And if it's a company where that kind of information is "secret" and not disclosed to the people who are enforcing it, that's a sick culture.
What I would argue is that (unless you're the bouncer at a nightclub) it is pretty shitty to refuse someone entry without explanation. If you don't know the reason, you should be willing to call your superior and find out, and maybe sort out the situation properly.
And if it's a company where that kind of information is "secret" and not disclosed to the people who are enforcing it, that's a sick culture.