To me it seems you imply that its OK to coerce certain people into taking certain work. I view the second paragraph as an attempt to justify that position, despite its conflict with basic humanist ideals.

Ignoring the hypothetical nature of your second paragraph, I think you miss the incentive to all "work", which depends on how much the worker thinks his work is worth.

Take my friend the farmer, who happily works on a tiny organic farm (hard physical work) for very little pay, because he feels his work is sustainable, and productive (helps others, provides food).

Also take my friend the construction worker, who would love to build houses for the rest of his life despite low wages, but won't, because he is unable to find employer that will enable his labor to bear fruit. Sure he could build mansions, and commercial monoliths to no end, embedding stone chipped from the Italian coastline into German upper class house-fronts, or build shopping malls. But he's not an idiot, he won't waste his life pouring his talent into luxury products and consumption infrastructure that won't help anyone in the end. He wants to build sustainable housing for people to live in, houses so cost effective everybody can have one.

Depending on coercion to motivate a work force, implies that the work to be done is actually detrimental to society.

Anecdotally speaking you're getting paid to exercise. If it weren't for the shit pay and the no health benefits I genuinely might go back to working part time as a rickshaw driver. I used to be a rickshaw driver and it was good work, and I was genuinely pretty happy. Also had plenty of mental energy available at the end of the day for thinking problems (which is why I said part time and not full time)