The author confuses criticizing a libertarian with criticizing libertarianism itself. Libertarianism itself is an extremely broad term, and in the US its meaning seems almost entirely connotative. That is, it seems to have no definite traits aside from the 'live and let live' attitude of those who profess it. To attempt a critique of libertarianism as a whole is thus difficult because everybody seems to define it differently, with no clear consensus going one way or another.

This means, Rothbard goes on, that a parent “may not murder or mutilate his child, and the law properly outlaws a parent from doing so. But the parent should have the legal right not to feed the child, i.e., to allow it to die.”

Thing is, most libertarians disagree with him on this. Rothbard isn't the King of Libertarian Thought, after all. He himself once observed that libertarian writers all seem to have at least one issue on which the rest of libertarians disagree with them. Rothbard's views on fractional reserve banking are also something most other libertarians reject.

There's also something of a bait-and-switch in this article. They quoted somebody from a blog titled NeverSayNothing, whose author (undisclosed) refers to Rothbard authoritatively as “the founder of modern libertarianism.” They then turn to Robby Soave, a writer for reason magazine, an organization whose work generally doesn't adhere to the Rothbardian school of thought and whose writers would tend to have been less influenced by Rothbard's views than the writers of the NeverSayNothing blog (who in a followup article claims “the non-aggression principle is the basis for libertarianism”). I think they were hoping people wouldn't bother looking at the sources and just assume that the same self-titled libertarian went from calling Rothbard the founder of libertarianism to treating him like his views don't matter, thus furthering the narrative that libertarians constantly move the goalposts to make their ideology impossible to define, when in reality it's just that they were quoting two different sources who happen to disagree on the matter.