The libertarian world of our pundit class is by definition an imaginary world, which cannot exist outside the heads of its believers. It is freedom without responsibility and without cost. Since that happy state can't exist, libertarianism is just a pleasant mental fantasy of an eternal upper-class adolescence, when they paid for everything with Dad's credit card and had nothing to do but show up at private school. Now they don't want to pay taxes and they don't want to work to make their world better, they just want to coast on someone else's dime and go out for drinks.
Nothing else is real to them because reality interferes with the happy fantasy. Megan McArdle's father had jobs in public works, privatized public works, and lobbying. He worked on government sanitation projects, so McArdle knows that the government can succeed in its endeavors. McArdle knows that money buys advantage and there is no free market. McArdle was hired by her father and his contacts and she knows that the world is not a meritocracy. McArdle knows that private companies can be corrupt and wasteful. None of this matters--it doesn't even exist for her because nothing has to be real in her world. She simply believes what she wants to believe, whatever flatters her idea of herself and helps her live with herself. It's what authoritarians do to survive. Some turn to God, some to politics, some to hate-mongering, but they all are driven by forces they don't know exist. Their advice is erratic and often wrong, their morals are flexible, and their overwhelming desire to be liked and praised regardless of merit makes them utterly unreliable.