He is a great American hero and Medal of Honor winner. He served during a period mainly in the 1920s and early 1930s in Latin America. Marines call that period the “Banana Wars”. The Banana Wars were the occupations, police actions, and interventions on the part of the United States in Central America and the Caribbean between the end of the Spanish–American War in 1898 and the inception of the Good Neighbor Policy in 1934.
However, this was before World War II. The Marines, and other servicemen that fought that war fought against fascism. In 1935, in his book War is a Racket, he denounced the role he had played, describing himself as “a high class muscle man for Big Business, for Wall Street and the bankers…a racketeer, a gangster for capitalism”.
You can read the information for yourself, there is certainly some truth, to what General Butler said about some of the things he saw. But not in total.