Scouts Out! Cavalry Ho!
Give me several hours to construct a "libertarian society thought experiment" and I bet I could change your mind.
But we don't have several hours, and as things stand with our current welfare state open borders are totally impossible. That's the point I was trying to make.
If you pull one part of the platform out of context, it often looks ridiculous. Unless all of it were enacted, other parts are clearly not practical. It's a logical totality. Open borders depends very much on that totality. In our current situation it'd be suicide, either fast by terrorists or slow by parasites.