During the height of the McCarthy period Ewen was forced to resign his teaching position after refusing to cooperate with a Senate Internal Security Committee investigation of communism and higher education.
His first book, The Prestige of Schiller in England, based on his doctoral dissertation, was published by Columbia University Press.
Ewen was appointed assistant professor of English at Brooklyn College in 1930. he joined the Teachers Union shortly thereafter and was involved in left politics on campus and within the larger movement in New York City.
After being forced to leave Brooklyn College, Ewen assembled a team of blacklisted actors, including Ossie Davis, Ruby Dee, and John Randolph to present dramatic readings of great works of literature.
When the repression of the McCarthy era began to lift in the early 1960s, Ewen, along with Phoebe Brand and John Randolph, produced an adaptation of James Joyce's Portrait of the Artist as a Young Man, which had a two-year run (1962–63) at the Martinique Theatre in New York City.
At the time of his death, Ewen was working on a second volume, which appeared posthumously as A Half-Century of Greatness: The Creative Imagination of Europe 1848–1884.
[6] These two volumes explore the relationship between Marxism and Romanticism, the politics of protest and revolution, and the European literary tradition.