Borders. Imaginary lines. I can understand them to a certain extent. Private property lines are the borders that trump all others. And I can even understand a "border" that gives an area an identity. Maybe based upon geography or customs or other things like that which give a shared identity that the locals rally around. As long as they are not imposed or maintained by "law".
What I don't understand are "legal borders". I mean the kind that derive from governments saying "We have these laws over here, and they have those laws over there. Our laws are better than theirs." That includes saying that "You live here, so we are entitled to a percentage of your money." And, really, that's all "national borders"- and even "state borders"- come down to. "Our laws are better than their laws" and posturing to be the "legitimate" thief.
To say "Here, possession of this plant/gun/car window makes you a criminal, even if over there it doesn't" is evil. For that matter, passing or enforcing any "law" that attempts to control or prohibit anything beyond aggression or taking/damaging property (which may include trespassing) is evil. So, arguing over borders is just two thugs arguing over which one is violating you in "just the right way".
And the short answer to that is: neither one.
Since I don't believe in "laws" that go beyond (or violate) the Zero Aggression Principle and "don't steal/damage other people's property" (which never need to be written down anyway), the rest of the "laws" are all bad. To pretend your counterfeit "laws" are better than anyone else's counterfeit "laws" is ridiculous.
It's not about "open borders". It's about the ridiculous notion that a line dividing between different bundles of "laws" is anything other than a delusion based upon elevating theft and aggression to a place of honor.