Some libertarians like to pretend they are neither right nor left. Maybe some are. Most, however, are either rightist-libertarians or leftist-libertarians.
The easiest way to tell them apart is their view of "Martin Luther" King, whose real name was Michael. The right sees him for what he was -- a plagarizing, woman-beating, whore-mongering Communist adulterer. The left thinks he was a good guy (which reminds me of what Erik von Kuehnelt-Leddihn wrote: "Leftists don't merely misunderstand human nature; they don't understand it at all").
Since leftists all all stripes don't understand human nature, they will of course have whacko ideas. One of those ideas that leftist-libertarians have is the idea of open borders, since they believe borders are "artificial."
That belief is the depth of silliness. What isn't artificial? Clothes? Houses? Cars? Domesticated dogs? Beaver dams?
These people can't even tell the difference between "natural" and "artificial" -- not that is matters.
Leftists also don't believe, in varying degrees, there aren't any significant differences between men, women, races, cultures, religions, ethnic groups.
Such beliefs are ideology -- and I mean this in the sense that Russell Kirk defined it: a set of simple-minded beliefs that people believe apply to everything, even if they clearly, obviously don't.
Kirk wrote that ideology is "a dogmatic political theory which is an endeavor to substitute secular goals and doctrines for religious goals and doctrines." What he wrote explains why deracinated "intellectuals" believe things no one with any common sense or experience in life would believe: get rid of government and borders and Utopia will blossom.
Since what leftists believe is their religion (and atheism is a religion) they can't change their minds (and that reminds me of the saying, "Insanity is doing the same thing over and over and expecting a different result").
Imagine if we did have completely open borders. We wouldn't have peace and free trade. There would be war and genocide. Anyone who thinks otherwise has never heard of the Hutus and Tutsis, the Europeans and the American Indians, the Romans and the Celts...or any other ethnic group that has tried to share the land with a different one, throughout all of recorded history. And, I'm sure, before.
Imagine Jews, Christians, Muslims, whites, blacks, browns and Asians all trying to share the same land...say in America. In the hallucinations of leftists all would get along, united in their love and SUVs and DVD players. In reality they'd kill each other until one tribe expelled all the others. It's been the history of the world. As the War Nerd so perceptively wrote, "When one tribe encounters another historically the result has been genocide."
Some libertarians quote Murray Rothbard, a good economist but a poor historian. He used the examples of Ireland and Iceland as "anarchist" societies. He didn't know much about them, and neither do his followers.
Iceland was an island of bloodshed and slaughter. And as for Ireland, I have forgotten more about than area (being that my ancestors are Scots-Irish) than Rothbard ever knew. For hundreds of years the area around Ireland, Scotland and Northern England was a land also of murder, theft and slaughter. The people were called Borderers, or reivers. They were probably the most fierce and war-like people in the history of the world -- and some of the dumbest. And they are my ancestors.
The only way there can be open borders is if the federal government overrules the states, counties, cities, neighborhoods, and people. And why do they do it? To enrich the 1% at the expense of the other 99% by driving wages down to rock bottom. To impoverish everyone so the superrich and become even richer.
That would be funny if it wasn't tragic -- the idea that libertarians, who supposedly hate the federal government, unwittingly support it. That's what the self-delusion of ideology does to people. It warps their brains and makes them unable to see reality.