Sugiyama is a Nanjing Massacre denialist, stating that the facts regarding it are "selective in nature". He was one of the signatories on "The Facts", a full-page ad published by "The Washington Post" on June 14, 2007, which was written by a number of Japanese politicians and academics in response to the passing of United States House of Representatives House Resolution 121, which sought an official apology from the Government of Japan regarding their involvement of using "comfort women", which were women who were used as sexual slaves by Japanese soldiers during World War II.