an open border presupposes the existence of said arbitrary borders.
This is an excellent point. I agree 100%. Thank you for elucidating that for me. I think this is maybe where the breakdown in communication between the two camps is happening. I am advocating the dissolution if the state, and thus, state "borders." The other camp often assumes I advocate state open borders. I do not.
That has to be where it's happening. I can't tell you how many people I've seen declaring emphatically that the state must be abolished only to turn around and declare "we" need "open borders." If the state is abolished, there's no border to open, so the argument for an open border is obviated. I'm glad I could help :)