I get that many people in prison did bad things. But we need to get past our petty feelings of revenge and hurting back people as "justice". We can do better.
The fact that it is for-profit, and thus there is pressure on those who run the prison to minimize the costand resources devoted to their prisons and to do what they can to keep their prisoners in prison, as well as to do what they can to encourage the politicians to keep making laws that keep people in prison... all of which needs to be considered and potentially corrected.
That isnt to say that a private sector for-profit prison system cant work. In theory it can, but only with the right sorts of checks on those interests.