The use of Esperanto in cinema has been discussed, for example: Esperanto and Cinema. One example, which has been documented in various places, is the film Idiot's Delight. (The Esperanto version of the Wikipedia article does not give an adequate explanation for the use of Esperanto in the film). In a recent historical work, the political context is outlined:
Throughout the film industry's relatively brief existence, moviemakers—protective of their profits and worried about private pressure groups and government censorship—had done their best to avoid controversy. They were particularly concerned about not offending important foreign markets, which accounted for at least half their annual revenues. In the 1930s, Germany and Italy were key outlets for American movies, and studio heads were reluctant to do anything that might anger those countries' totalitarian leaders.Robert Sherwood was made aware of that fact when his Pulitzer Prize-winning play, Idiot's Delight, was optioned by Metro-Goldwyn-Mayer in 1936. Both antiwar and anti-Fascist, Idiot’s Delight, set in a small Italian hotel on the Swiss border, focuses on a disparate group of international travelers who are stranded when Italy launches a surprise air raid on Paris. To avoid annoying Italy, the head of MGM, Louis B. Mayer, ordered the story's setting changed to an unnamed country whose inhabitants spoke Esperanto instead of Italian. There also was to be no mention of Fascism. The Italian consul in Los Angeles was given final script approval, and MGM previewed the film for representatives of the Italian government.
When Sherwood, who wrote the screenplay, was asked if he had had any collaborators, he ruefully replied, "Yes—Mussolini." Expurgated and defanged, Idiot's Delight was roundly panned by the critics when it was finally released in early 1939. And despite all MGM's efforts to placate Italian sensibilities, Italy ended up banning it, as did Spain, France, Switzerland, and Estonia.SOURCE: Olson, Lynne. Those Angry Days: Roosevelt, Lindbergh, and America's Fight Over World War II, 1939-1941 (New York: Random House, 2013), pp. 362-363.