ignoring Matt, this is not slavery, this is indentured servitude, which is different in several ways in that those under contract would be freed after a given period of time and they would be housed, fed, and paid, all of which is what's happening here
so to call it slavery is ignorant if not biased against the agency
as for private prisons, yes I'm against them, the recidivism rates alone are enough to turn me off to the idea
but having prisoners work? aren't you prison reformers talking about giving these people the skills to do well in society? so they can't work for their crimes but they can get an education? seems kind of hypocritical to me, besides it'd be better that they be worked to their limits rather than them beat the stuff out of each other and assforget the weaker ones some more