Because it’s intellecually dishonest and an argument based on the fallacy of appeal to extremes.

There is obviously a difference between citizenship and race... the entire purpose of a government is to service its citizens. Unfortunately, we don’t live in a Star Trek utopia where there is free movement of all people. If one country were to allow this first, they’d just be harming themselves, which would be against the interests of its citizens. You look out for your own citizens first. That’s just a government fundamental.