The people who were involved have said many times that certain actions were forestalled or interdicted because of the information given through the use of waterboarding.
In addition, there is no permanent psychological or physiological harm done to the individual waterboarded. We use the same type of event to train SERE personnel.
McCain can go back to his retirement home in AZ and pickle himself for all I care.
That or one of his other five homes. Or is it seven? Nine?