There's a lot to untangle here, and in your article. The supply/demand question reminds me of a seeming paradox about gentrification -- that a young professional (or artist) who moves to that up-and-coming neighborhood appears to be the one at fault, making the place more expensive, creating more churn, becoming another patron for the lifestyle shops. Similarly, it's tempting to blame the adjunct, as you suggest -- that by accepting the adjunct jobs they allow the system to survive. Your article also suggests blaming the careerist tenured academic for moral compromise: "The cost to the individual who manages to get tenure is low but the cost to the field as a whole is high."

While I share your moral outrage, I see these phenomena -- whether the dilution of academia or the dilution of vital neighborhoods -- as a series of top-down structural choices. That gentrification is the result of opportunistic investment and regulatory capture of local governance. That starving adjuncts and uninspired professors are the result of a devaluing of a liberal arts education in the name of a bottom-line STEM/entrepreneur-centric view of what is valuable to society. That a get-your-act-together chiding of those screwed won't correct a system willfully rigged to take advantage of the idealist.

All this to suggest that we shouldn't blame the victim, whether that is the adjunct or the badly taught and overcharged student, for having hope in teaching, learning, and an uneconomically rewarding practice.