Jonathan Chait brings it all together for me.
There are just a lot of people out there exerting significant influence over the political debate who are totally unqualified. The dilemma is especially acute in the political economic field, where wealthy right-wingers have pumped so much money to subsidize the field of pro-rich people polemics that the demand for competent defenders of letting rich people keep as much of their money as possible vastly outstrips the supply. Hence the intellectual marketplace for arguments that we should tax rich people less is glutted with hackery.
A “free market” explanation for desperate right-wing hackitude. There simply aren’t enough qualified partisans hacks on the right to construct somewhat valid arguments! It explains so much.
Most people don’t follow these issues for a living and have a hard time distinguishing legitimate arguments from garbage. I don’t mean this patronizingly: I certainly would have trouble distinguishing valid arguments from nonsense in a technical field I didn’t study professionally. But that’s why there’s a value in signaling that some arguments aren’t merely expressing a difference in values or interpretation, but are made by an unqualified hack peddling demonstrable nonsense.