I am criticising, specifically, the notion that a piece of paper 'qualifies' some part of some group to comment on X discipline, and the lack thereof 'disqualifies' some part of a different group from commenting on X discipline.
This notion is fine (generally) in the hard sciences and engineering. In other disciplines, the social 'sciences' particularly, this notion is risible.
I am distinctly NOT defending bloggers, on economic analysis or anything else. I am stating that anyone disqualifying a blogger (or any one else) sine papyro de facto is an utter jackass.
It "qualifies" someone the same way it "qualifies" a medical doctor to comment on a particular health condition. That's not to say a particular blogger is incapable of providing insight (and the author goes out of his/her way to emphasize it), just that when you're sick, you go see a doctor. Ask yourself, why do you do it?
Moreover, the author admits some economists are quacks, just like some doctors. You're really making a mountain out of a molehill.