Earlier quoted context omitted.
You realize that the number of people in jail and prison labor are orthogonal issues, right? One can both oppose our war on drug users (near as I can tell, the main source of our excess prisoners) and China's war on the Falun Gong, but also have no objection to forcing robbers/rapists/murderers to work for their keep.
They are most certainly not. Presumably the base rate of bad people in the human population does not vary greatly from country to country, yet the rate of jailed people does. It follows that many people in jail in countries with a high rate of incarceration arguably ought not be there; and making life harder for them is wrong. Or to put it another way, arguing from justice, along the lines of Rawls' original position…
That's an empirical question. I wouldn't presume one way or the other on that issue until I had some data. (I would, of course, have to define "bad people" in some reasonable way that would work cross-culturally to gather my data.)