1. Waterboarding is not what the Gestapo, KGB and North Vietnamese used. While it does induce panic and is certainly anything but pleasant, you misrepresent what it is to lump it in with the atrocities properly called tortures.
2. How painful a death do you think people caught in the fires at the World Trade Center had? If you are opposed to humans being caused to die that way and you could have saved 3000 people by waterboarding a much smaller number, would you have said, "No?"
3. I understand that torture is inhuman and that we can't justify returning torture with torture. I do not criticize your revulsion towards torture, but you must answer the above points.