Too often I see people argue "X is a social construct" as a way of arguing that X "doesn't exist", or that people who believe in it have a kind of false consciousness.
I'm trying to show why people believe in it. Yes, it's a social construct; but that doesn't mean it's worthless - "money" is also a social construct: it only has value because other people think it has value.
The nation appears to be the largest stable unit of organization humans are capable of, at present at least. The history of the world has shown that Empires don't last too long these days.
I don't think anyone disputes that nations are social constructs, it is the "and as such all immigration policies of any sort are illegitimate and harmful." part that is controversial.
It's not very useful to stress that they're "artificial" unless you're trying to introduce the term for rhetorical effect, say, edging it into the discussion on narrow or technical but not especially useful or broad applicability, relying on implications of the word or other, far less relevant meanings or shades of meaning to have an effect on listeners/readers. This happens a lot, especially in political discussion. It's sloppy as hell and should put you on high alert if you catch someone doing it, especially if they should know better.
Yes, the problem is with the "artificial" part. Lots of things are social constructs but that does not that mean that you can dismiss them as automatically illegitimate.
Who said illegitimate? I take artificial in this context to mean not inherent, so like if you ran history over again the nations people have organized into over the centuries would be different.
The second part of the statement was "and as such all immigration policies of any sort are illegitimate and harmful.", which seems to be being ignored by those who want to claim that the fellow was unreasonably complaining about nations being considered as social constructs.
A Schelling point for coordinated actions by large groups of people, organized around ethnic, cultural, and/or linguistic grounds?