I don't see why that follows, considering they're two different things. In any case I do think prisons themselves are one of the blights of modern society.
While I'm not certain that society doesn't have the authority to force people to work (though, if it is ambiguous/uncertain, I would advise "don't", and I am not confident it does, so I advise "don't"), but I do agree that it doesn't really seem to follow, at least not without assuming some other premises.
