No one likes to be reminded of their biases.
I am actually grateful that someone cared enough to write what appears to be a thoughtful article on the subject. I have been mystified by this phenomenon for years. Ask someone: "Do you have a car?" If the answer is in the affirmative, say, "Oh, then can you tell me what increase of the torque on the wheels I will get if I double the pressure in the cylinders?" Most people would reply as if you offended them: "I don't know. Why are you asking me? I am not an engineer?"
You would arrive at the same outcome if you were to ask a similar question about ironing, or light in the room --- practically anything. People understand that they cannot learn car dynamics no matter how long they drive the car: they need to study mechanical and aeronautical engineering. They understand that one cannot explain how the iron gets hot even after ironing for years: some physics is needed for that.
I found only two, notable in my opinion, exceptions: administration (""my manager is so stupid," such and such CEO "has ruined the company by ___", etc.) and economics. In contrast to all other areas, people assume that they can understand management without any study, just by observing their own managers. They are equally convinced that they understand economics just because they have experience of acting as economic agents. I have never understood why this is the case and continue to be puzzled by this.
In sum, I can imagine how people react to what this author appears to be saying: there is more to economics that meets the eye' it ain't simple, so you need to study --- preferably all the way through a doctorate. They'll roasted him with salt on high heat just for that, even if he avoided self-selection and moral hazard.
They want to remain (armchair) generals without going through the rigors of a military academy.