I think Dos Passos had ceased to be a communist at this point. He was one of those disillusioned by the Spanish Civil War who then became a "premature anti-Stalinist" and was denounced by his former comrades for breaking with the Party line.
Whatever he believed in the '30s, Dos Passos was a clear-eyed enemy of communism post WWII.
No matter,he was still a damned lefty fifth columnist and a terrible play-write/author.
Isn't it just amazing that so few Americans have any comprehension of history? It's not just that they can't name who was President during the Civil War, or in what decade of what century the Spanish-American war was fought ... no, they don't have any memory or understanding of the history of the 20th century and the Second World War. Even many of the people who SHOULD know better because they lived through those years are utterly clueless.
God deliver us from the historical amnesia of the American population! Those who forget their history are doomed to repeat it.