He was saying if they acted like barbarians we could and that any means we cna use are legitimate.
And YES waterboarding is barbaric and against international law. It's totally irrelevant who the person is:
"All nations that are signatory to the United Nations Convention Against Torture have agreed they are subject to the explicit prohibition on torture under any condition. This was affirmed by Saadi v. Italy in which the European Court of Human Rights, on 28 February 2008, upheld the absolute nature of the torture ban by ruling that international law permits no exceptions to it.[168][169] The treaty states "No exceptional circumstances whatsoever, whether a state of war or a threat of war, internal political instability or any other public emergency, may be invoked as a justification of torture".[170] Additionally, signatories of the Universal Declaration of Human Rights are bound to Article 5, which states, "No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment".[171] Many signatories of the convention have made specific declarations and reservations regarding the interpretation of the term "torture" and restricted the jurisdiction of its enforcement.[172] However, UN High Commissioner for Human Rights, Louise Arbour, stated on the subject "I would have no problems with describing this practice as falling under the prohibition of torture", and that violators of the UN Convention Against Torture should be prosecuted under the principle of universal jurisdiction.[173]
Bent Sørensen, Senior Medical Consultant to the International Rehabilitation Council for Torture Victims and former member of the United Nations Committee Against Torture has said:
It's a clear-cut case: Waterboarding can without any reservation be labeled as torture. It fulfils all of the four central criteria that according to the United Nations Convention Against Torture (UNCAT) defines an act of torture. First, when water is forced into your lungs in this fashion, in addition to the pain you are likely to experience an immediate and extreme fear of death. You may even suffer a heart attack from the stress or damage to the lungs and brain from inhalation of water and oxygen deprivation. In other words there is no doubt that waterboarding causes severe physical and/or mental suffering– one central element in the UNCAT's definition of torture. In addition the CIA's waterboarding clearly fulfills the three additional definition criteria stated in the Convention for a deed to be labeled torture, since it is 1) done intentionally, 2) for a specific purpose and 3) by a representative of a state– in this case the US.[174]
