“Making a film attacking Hitler [‘The Great Dictator’] proved far more controversial than Chaplin anticipated.

”Producers who wished to turn out starkly anti-Nazi movies—such as Walter Wanger, and Harry and Jack Warner—were repeatedly constrained by Hollywood's self-censorship board, the Production Code Administration (PCA), and its anti-semitic head, Joseph Breen. Created in 1934 to forestall federal censorship of motion pictures, PCA rules prohibited filmmakers from attacking or mocking foreign governments and their leaders. When Hitler and Mussolini promised to ban the films of any studio that offended them, and all Hollywood films if necessary, Breen stepped up his efforts to stop producers from endangering the industry's highly profitable foreign revenues.

“Indeed, not everyone thought Hitler was so evil. As late as January 1939, PCA censors attempted to halt production of Warner Bros.' Confessions of a Nazi Spy, the nation's first explicitly anti-Nazi film, explaining that to ‘reperesent Hitler only as a screaming madman and a bloodthirsty persecutor, and nothing else, is manifestly unfair, considering his phenomenal public career, his unchallenged political and social achievements, and his position as head of the most important continental European power.’”

—from “Hollywood Left and Right: How Movie Stars Shaped American Politics,” by Steven J. Ross

According to the Production Code Administration, Hitler had “unchallenged political and social achievements.” Why pick on him? According to HUAC 10 years later, the star of the movie was a red, too.