Why did proponents of the torture memo believe that waterboarding was an acceptable interrogation technique?. . They argued that waterboarding was used in multiple conflicts throughout the twentieth century.. . They argued that waterboarding was not considered torture in countries like Iraq, so could be used by the United States.. . They argued that the president had the authority to do whatever he deemed necessary to get information in the global war on terrorism.. . They argued that Congress had not specifically outlawed waterboarding, so it should be upheld as a useful tactic..