>Your context changes nothing: it's just one long "the ends justify the means" or "that's the way it is" and fails to address any of the ethics of the statements being made.

Is it asking too much of you to drop these thought ending cliches and actually try to argue your case? Ultimately ethical claims must bottom out at premises that can't be further supported. Here's the ethnical principle at play in my view: the freedom of association is a core principle as is its corollary, the freedom to dissociate. Just as I can exclude anyone from my home in principle, we can collectively exclude anyone from our collective land. This is the principle that justifies a nation discriminating based on citizenship. Of course, scaling from kinship groups to mega societies requires scaling these processes to something impersonal and ideally fair. Laws are the solution to this, but laws just are a representation of collective action and so inherit their justification.

>Why? All immigration systems I know take the person's views into consideration (for obvious reasons).

Yes, nations take stated/purported views into account. The issue is that it is impossible to accurately determine each immigrants personal views at scale. The inherent uncertainty involved is a risk, one that a host nation need not accept.

>They can't do that without disregarding the equality of all humans as a universal principle.

Universal human equality does not trump the right to free association/dissociation. Just because I see you as morally equal to me in principle does not mean I must suffer your presence around me. Of course, interpersonal relationships are different than laws. But laws are inward facing. That is, they create duties to and between people who are part of the same body politic. Outside of that body politic one has limited duties to each other. A right implies an obligation; a positive right is a claim to the effort/resources of others. I deny the legitimacy of universal positive rights. The only legitimate universal rights are negative rights, i.e. freedom from interference, assault, etc. But this doesn't imply freedom of movement across political borders.