A lot of libertarians remind me of militant atheists: won't shut up, are convinced they know the truth, and believe it'd be a much better world without religion (except for the religion of Atheism and Evolution).
The more rabid of libertarians (i.e., the ancaps, or anarchocapitalists) have two obsessions, and both are dangerous: corporations and open borders.
They support such Cosmodemonic Transnational Megacorporations as Wal-Mart, believing they are free market. No corporation is free market, and in fact they are the opposites of the free market and want to destroy it.
Corporations are creations of the State and have been since their beginning several hundred years ago. I'm going to repeat this: they are not free market. They were never intended to be. Many don't know that corporations have the legal status of a person: they are legally "people," and as much are immune from many laws.
Most people believe the first War of Independence was caused by "taxation without representation." Nope. It was caused when the East India Company (aka John Company) was given a tax rebate of millions of pounds from the Crown to run out of business their American competitors in the tea market.
That's what caused the Boston Tea Party. And the East India Company was the largest international corporation of its day. Imagine McDonalds and Wal-Mart rolled into one monster.
Mussolini defined fascism as Corporatism - the State plus Corporations. Because, ultimately, they are the same thing. That's what caused the first War of Independence - fascism. The State plus Corporations.
When you tell the most fanatical of ancaps these facts, they don't believe it. They'll still fanatically defend corporations. And that is why there exists the saying: there is none so blind as those who will not see.
Now we've got the open borders fanatics. The State plus Corporations (the fascists) support open borders to flood the country with illegal immigrants to drive wages down. Open borders doesn't help the economy or the culture: it damages both (although the fascists lie and say they do).
In other words, when "libertarians" support open borders they're supporting fascists. Again, they absolutely refuse to believe this.
For that matter, an ancap society could not exist. Ancaps are leftists, too confused to know it, and like all leftists they don't understand human nature. Like all leftists, to them the solutions are simple. In reality, they're merely simple-minded.
Libertarianism isn't even American. Thomas Jefferson was a classical liberal (which has nothing to do with psychotic leftist/liberalism of today), and all of them believed in some form of government. Not one was an anarchist.
Even Rose Wilder lane, touted as 20th century libertarian, believed in the "slightly restrained" free market. The only ones who were close to being anarchist were the ones least American: Ludwig von Mises and Murray Rothbard (who wrote abortion was okay because the fetus was "a parasite).
If we were angels we wouldn't need government; if we were devils it would never work under any circumstances, and since we are in-between, there will always be government, but it will never work the way it should.
There has never been an ancap society in the history of the world. Murray Rothbard, a second-rate historian, claimed Iceland and Ireland were anarchist societies. The only thing that shows is that Rothbard didn't know anything about those savage, murderous, backward societies.
Anarchocapitalism is DOA, and they did it to themselves. They only way they can resurrect it is to call for the elimination of corporations and to oppose open borders. As things stand now, they're supporting fascists, but are too dimwitted to know it.