A person is morally entitled to privacy in their own home. Whereas national borders seem convenient for exerting control over our environment, the problem arises when we keep people in or out for arbitrary reasons. That’s what the debate is about.

I can keep people out of my home for arbitrary reasons because I have inalienable rights. But nation states have neither rights nor moral authority of any kind, unlike the individuals inside and outside their borders. Specifically, citizens have the right to interact with anyone (sans coercion), regardless of where they were born. This basic liberty is infringed when borders are closed.