alt Hacker News>How is that not arbitrarily discriminatory on its face?
A nation discriminating against non-citizens is not arbitrary, it is the core feature of the citizen classification. What you are implying is that the concept of "citizen" is unjust, therefore the concept of countries and borders are unjust. Of course when its put into these words few people will cop to this viewpoint. That's why there's endless obfuscation in these discussions, to avoid articulating the plain truth of your views.
It is arbitrary if you believe all humans should be afforded the same basic human rights and should not be judged simply by the country they come from (rather than the content of their hearts, minds, and character).
Do you believe that if a country can discriminate or harm non-citizens, then it should do that? Is it morally/ethically correct to treat non-citizens less than other persons?
Do you hold beliefs that apply to all people regardless of what group they come from or only your own tribe?
It really does simply boil down to whether or not you believe all humans should be afforded the same basic rights and considerations. The "citizenship" argument is essentially a legal loophole to claim that whatever the law says is the moral/ethical path, which it is not.
Laws can be (and often are) immortal/unethical, so grounding your argument in what is currently legal or not is a bad look (as it has always been); just ask former slave owners about the morality/ethics of the law, and see where that gets you.