When your parents said you could be whatever you wanted to when you grew up...The link in the OP in no way limits the "open borders" concept to moving/living to/in another country. It's the movement from one country to another for a plethora of reasons. Could be to live. Could be to work. Could be to visit.
I thought the last two paragraphs were good. The severe lack of human empathy surrounding the immigration argument is pretty stunning, at least from the majority of this forum.