There's a rebuttal for everything if you look.
According to the ACLU 7% of state prisoners and 18% of federal prisoners are in for-profit prisons[1]. Federal prisoners make up less than 20% of the total prisoners. So a minority of a minority are prisoners of the federal "prison-industrial complex".
I of course also hear the rebuttal that public prisons are supplied by private companies. Which is of course true. The government does not grow food or produce security cameras. Perhaps we'll accuse Georgia Pacific of being a beneficiary of the "collegiate-industrial complex" as well as the "prison-industrial complex" because they supply paper products.
I believe our prisons are broken. I believe our prisons are cruel and immoral. But I do not believe there is a vast conspiracy of private interests locking people away for the sake of profit. Nor do I believe that those interests influence our politicians in any meaningful way.
Ask yourself, is it likely that our politicians are completely beholden to an industry that makes up a fraction of a fraction of a percent of our economy? Or is it much more likely that our representatives believe private prisons could, should, or do work?
1. https://www.aclu.org/issues/mass-incarceration/privatization...