Who will be the judge on what they deserve? How would you measure by metrics someone else's pain? What about the potential abuse of these methods by future governments? Also, do you even support the Geneva conventions?
Read the links provided by taks, they pretty much sealed the deal.
What do your first three sentences have to do with anything? And yes, I support those Geneva conventions which the US signed. Those apply only to uniformed soldiers fighting for a country which itself had signed the Geneva conventions. Thus Japanese soldiers were prosecuted because they had no right to do what they did under the Geneva conventions. Moreover, they did a lot more than waterboard, they beat and starve out soldiers, who were legal and legitimate prisoners of war. All the procedures approved by the Justice Department for terrorist interrogations are done to our soldiers as well, as part of their training to prepare them for possible capture and interrogation.