Are they suggesting authoritarian communism or some sort of sci-fi anarchist communism? (which would be pretty pro-individual-liberty).
Open borders seem pretty pro-liberty as well. What’s more authoritarian than a government telling you there’s a magic invisible line on the ground and if you cross it, that’s crime?
It's not magic and it's not invisible. And if it's a government for the people, then it's the people that are being authoritarian. Maybe a high-liberties society can only prosper if it protects itself from the outside.
Nations are a social phenomenon and only sometimes line up with borders. States are what define borders (in fact it's part of the definition of a state).
Open borders seem pretty pro-liberty as well. What’s more authoritarian than a government telling you there’s a magic invisible line on the ground and if you cross it, that’s crime?