I didn't need to read far to see this error in the essay. He notes that his goal is to refute Misesian and Rothbardian theories, acknowledging that it may be controversial to exclude Hayek from the Austrian perspective. Perhaps Dr. Caplan has other essays harpooning the Hayek stances, but all I see here is guilt by association.
Now, certainly we shouldn't damn the author for choosing a well defined system to distinguish himself from. Remember this is an article to commemorate his full-spectrum shift from Austrian to modern neoclassical economics, so it seems appropriate in a sense to choose the theories he first discovered. I propose that theories evolve with new information and fresh ideas becoming quite different over time than their progeny. There is value, for example, in defining all matter as atoms surrounded by rings of electrons. We know from continuing research that this is not exactly the truth, but the pictures are so nice that we keep using them (alternatively, it does a well enough job explaining phenomena that we keep it around). Incidentally, the purpose of the article is to explain how new observations cause old ideas to be adjusted. We need only hope the schools of economic thought would agree.
I tend not to agree with the diehard Austrians, but their system of analysis should be recognized as a potentially helpful one. Logic and praxiology have a place in any discussion, and blanket rejection of such methods only helps boost egos. Camilla wrote last week better than I am able: "I want to recognize that if economics is to be taken seriously it needs to have an approach that utilizes multiple angles." The Misesian and Rothbardian flavors of economics are absolutely valuable when the assumptions of the analysis are kept in mind. So are the views of Hayek, and the Keynesians, and even the socialists should probably receive credit for some thoughtful contribution to our views. If our ideas are not flexible, we can never be.