Atomist nonsense, but it's reason.com so I'm not surprised. That site is basically a gaggle of moral relativists; the equivalent of ivory-tower champagne socialists, but on a side of the spectrum that happens to dislike economic redistribution.
Again, simple logic demonstrates how hypocritical these ivory tower "conference libertarians" tend to be. By the logic of this Somin person, the family is also an "arbitrary" distinction. All communities are "arbitrary", then, so we should... what, dilute them endlessly?
The "argument" here is literally the same as "[x] is a social construct"! That's how openly lefist radicals phrase this particular form of madness. The crypto-leftist radicals like Somin avoid that phrase, but arrive at the same insane conclusion.
Yes, one could view the current child support laws as likewise being a form of hereditary privilege. After all, they give some children a much better quality of life relative to other children simply based on who these children's biological parents are--and also based on how exactly these children were conceived (through intercourse, through medical/clinical artificial insemination, or through at-home artificial insemination). When a parent voluntarily consents to these obligations, then this can be viewed as a gift from a parent to a child, but when a parent is forced to assume these obligations, then this would likewise be a case of governmental/state coercion in order to maintain a system of hereditary privilege.
Certainly. But even then, it is unwise to just open the borders without reservation. In a highly libertarian society, I suppose you could tie it to personal responsibility. Invite someone in, and they become your "charge". That is: any newcomer can enter by being "sponsored" by a private citizen... who then becomes responsible for the migrant's good behaviour. The sponsor not only has to pay for the migrant, but is also considered jointly accountable for any crime the migrant may commit. So, for instance, if the migrant rapes a women... both the migrant and his sponsor are executed.
That ought to encourage a bit of careful deliberation!
Libertarians would also say that such a policy should apply to births for the sake of logical consistency! But of course the problem is that a population can't continue without either births or replacement--and the former is much more vital for population continuation than the latter is. I don't know of any societies that have zero birth rates and total population replacement through immigration, after all.