He participated in World War II as a Naval photographer in the Pacific theater, serving in the same aerial photo group as George H. W. Bush. In 1982 he read the book At Dawn We Slept which contained allegations that challenged the official line about Pearl Harbor. He went to Pearl Harbor to investigate and write a news story. After more than 10 years of further research, and a lot of requests to the United States Navy under the FOIA, in 1995 he uncovered a 1940 memo discussing a plan to entice Japan 'to commit an overt act of war' against US, to crystallise public support for joining World War II. His claim that this plan was adopted personally by Franklin D. Roosevelt, and that the truth was kept from Navy commanders in Hawaii, has naturally proved inflammatory.

He is currently a research fellow at the Independent Institute in Oakland, California.

Previously, in 1982, Stinnett was working as a sports photographer for the Oakland Tribune newspaper. With 4 seconds left in the Big Game (football game) between Cal and Stanford, Stinnett stationed himself behind the South End Zone in California Memorial Stadium, at Berkeley. As it happened, Kevin Moen and teammates Dwight Garner, Richard Rodgers, and Mariet Ford pulled off "The Play", in which Moen fielded the Stanford kickoff, lateraled the ball, and five laterals later, received the final lateral, which he ran into the end zone through the Stanford Band. Stinnett was in perfect position for a famous photographic shot wherein Moen is on the zenith point of his leap, roaring in triumph, the football held high over his helmet, and about to land on Stanford trombone player Gary Tyrell. While Stinnett's work on the Pearl Harbor issue is of greater historical significance, the Big Game photograph of Moen and Tyrell of 11-20-82 is also of some historical import, particularly as it marked the final play in a century of University of California football.