Where else are they going to be trained? Hollywood can only do so much and there’s nothing quite like talking to an actual rapist / murderer / violent robber / kidnapper / you fill in the rest.
Most guys, when they go to jail for minor crimes, just want to serve their time and get out. They are minimal risk inmates.
However, the way the US prison system is set up, those who are relatively peaceful are forced to become violent or predatory just to survive and that is unacceptable.