I don't understand this point of view. At least in the US a very large portion of the prison population are in jail for non-violent crimes related to drug sales and/or possession, and are being imprisoned unjustly. Some if not all "white collar" crime prisoners should probably also not be imprisoned. I for one certainly do not see jail as having any sort of innate "goodness" or nobility associated with it. It's a horrible, brutal, inelegant hack at best, and a travesty of justice in many cases.
Even those innocent of any crime?
"To make a blanket statement like "[Contributing to keeping prisoners in prison] is in no way an inherently good thing" is just madness."
His statement isn't a blanket one, for reference the one you used which I quoted above is a blanket statement. For his statement to a blanket statement it would have to be phrased something like "Contributing to keeping prisoners in prison is an evil thing to do". Which is clearly neither what he said nor meant.
... while simultaneously violating the agreements they signed with insurance providers and putting themselves out of business?
I don't know about you, but I want prisoners to stay in prison. To make a blanket statement like "[Contributing to keeping prisoners in prison] is in no way an inherently good thing" is just madness.