I didn't understand why this argument had to be made because it is so obvious to any voluntaryist/anarcho-capitalist that state borders are simply a violently enforced fiction, just like any other state "authority." Anyone who thinks there is any legitimacy to "public" property or state borders is simply a statist rather than an anarchist. I understand that there is at least one formerly respected anarchist thinker who has become a statist and Trump supporter (which is a great tragedy), but I didn't realize there were so many statists calling themselves voluntaryists. I thought calling for "open borders" was the same as recognizing the non-legitimacy of state borders, but now I understand that they are very different stances and the cause of much misunderstanding.