The full-time vs. adjunct debate has nothing to do with whether college is over- or under-supplied. It's a problem with how colleges supply whatever it is that they supply.
I am talking about professors since that is what the article is about and completely not worrying about colleges since that is off topic.
The entire point of the article is that a person who decides to get a PhD in history should be paid because they went to school for 4 years. To me, that concept is ridiculous and people don't get to be paid a lot for what they want to do in the absence of basic economic theory.
Too many professors, not enough demand = low pay. It sucks that person made that choice, but there are plenty of secretarial jobs which pay above poverty level which someone with a PhD in history could get.