The USA is kind of like the "Christian Vapers" forum. The borders are created initially to create a "sanctuary" for a group of people to have their own place, under their own rules. Over time, others will want to try to breach the borders, and they will be asked to leave, or made to feel unwelcome, if they do not meet the "standards" determined by those with power. Remember why the first settlers came to this part of North America - to escape the oppression and persecution they felt in England. The borders started out as a way to keep the British out as much as to keep the new colonists in. Humans may be wrong in their desires to create borders, but it inherent or else we wouldn't be at least somewhat territorial in nature.
They are only asked to leave if the break the rules/laws of the place to which they come. I think that is fair.