Trumbo's 1938 story and screen play, "Heaven With A Barbed Wire Fence."
The link far below is for "Heaven With A Barbed-Wire Fence," a 1938 story by Trumbo. It's interesting. Contains some intentional political and cultural messages, most films do. I don't understand why the boy isn't crazy about the girl, but maybe that's something Communists can explain too.
Based on the content of the film, you could not by today's standards say Trumbo was dangerous. You could however say that he was intent upon shaping audience political perceptions and attitudes with his screen plays. Whether other people in Hollywood like Frank Capra were doing this in the late 30's, I don't know. Capra was most certainly creating pro-American war propaganda after WW2 began.
Remember the context to the film. It was the later Depression years and about three years before Pearl Harbor. Communism was controversial, but not widely considered a danger to the world. A year after this film's release, John Steinbeck published "The Grapes Of Wrath," and in 1940 a film by the same name starring Henry Fonda was released. In it, people on hard times encounter and reject Communism, and later receive assistance from the federal government.
https://youtu.be/zfL8lUf0ZEM?list=PLeQ7rwUdKK_IaSBgVake80U3zg-xCMJHn