Now, this is a smart guy. On most things he is even beyond smart; he is wise. But here he has a giant blind spot that he seems to know is there and is trying to explain away. Yet the result is glaring inconsistency.
I don't believe in government's "borders". I do believe in property lines. I also recognize and accept that people are flawed. Including myself.
Do borders protect me from flawed people? No. Borders empower flawed people and give them more exciting ways to explore the depths of their depravity by violating others in myriad ways.
The only way I can imagine a "border" making a situation better is if the people "inside" had achieved a perfect society. Then it would make sense to defend a border to protect your society from the "outside" influences. But, then, if you need "protection" by restricting travel across property you don't own, by people who are not yours to control, your society wouldn't quite be "perfect", would it?
All people are flawed. All governments are comprised of some of the most flawed among a given population- those who think it's OK to attack and steal, as long as you do it "by the book" (or at least, while wearing the silly hat of government), and are attracted to that power. National borders are where these gangs of official criminals' territories collide. Sometimes that border is maintained by a truce- sometimes by threat. But, it's always just between the criminal gangs, not normal people like you or me. The borders are there to tell other governments that "These people are mine to 'tax' and control as I see fit. You use your subjects, I'll use mine!" Sadly these gangs brainwash some normal people into taking their side against their fellow residents. I have more in common with most "Mexicans" than I do with most "American" puppeticians and bureaucrats and enforcers/reavers. Thank goodness!
The claim that "right libertarians" accept that humans are flawed, while those of us who don't believe in "borders" don't, is ludicrous. It's a red herring of the stinkiest sort.
It just goes to illustrate, once again, that there is no such thing as "left libertarianism" or "right libertarianism". The "right" or the "left" in those labels are just an admission of the inconsistencies that are still being clung to- the areas where coercion, theft, or any other statist delusion is still accepted as valid. In those limited areas an otherwise "libertarian" individual is not being "libertarian" at all.