Uhm, many of these young men and women also happen to be violent felons. They are gang bangers, pimps, and drug pushers who think nothing of taking a young girl, getting her hooked on drugs and then using her as a prostitute to make money for the gang. They are not in prison to enjoy themselves. They are there to serve hard time from crimes against society.
I agree our prison system is imperfect. Worse, it's bad and it definitely discriminates to some degree. We need to find a better way to turn the lives of these young men and women around. But I do not think it is slavery. Slavery took innocents and turned them into less than humans, into property. These people are far from innocent.