To put the question another way: what are the professional obligations of someone who is expected to perform the work of a professional under conditions of deprofessionalization?That's from Invisible Adjunct, who has resumed publishing.
My economist's reaction.
To employers: You get what you pay for.
To employees: He who sells his product for a lower price know what it's worth.
The comments at the Invisible Adjunct post are worth looking at. I have reservations, however, about drawing parallels between adjunct appointments and apprenticeships, given the existence of a tenure track. There are, however, some old and mostly ignored principles on academic freedom and tenure that long-term temporary employees of academic departments ought to be more aggressive about invoking.