That’s pretty vague. They used to say that about someone who subsribed to a Union Newsletter. The primary argument against Chaplin back then was his proclivity for very young girls. Dalton Trumbo he wasn’t.
The National Council of American-Soviet Friendship (NCASF) was the successor organisation to the National Council on Soviet Relations (NCSR).
The 1930s witnessed the birth of the politically radical American-Soviet friendship movement which revolved around the Friends of the Soviet Union, founded in 1929. One of the major goals of the movement was for the United States and the Soviet Union to form an anti-fascist alliance. This eventually led to the foundation of the NCSR, which became the NCASF in 1941. The Council’s membership was largely made up of professionals sympathetic to socialism and communism.
Key figures
Corliss Lamont was one of the foundators and the first chairman of the council. Professor Ralph Barton Perry of Harvard University was vice-chairman of the council. Edwin Smith was the executive director of the council. Here’s timeline of NCASF office holders:[1]
Hollywood support
Charlie Chaplin was one of the sponsors when the founding of the council was announced in April 1943. when an “American – Soviet Friendship Rally” was held in Madison Square Garden on 16 November 1944, a number of Hollywood movie stars — including Chaplin, John Garfield, Rita Hayworth, Orson Welles, James Cagney, Katharine Hepburn, Gene Kelly, and Edward G. Robinson — signed a message in a gesture of support. The statement said that the artists added their voices in favor of the bond that existed between “our great country and our great Allies.” The message added: “In this friendship lies not only the hope but the future of the world.”[2] ...”
http://en.wikipedia.org/wiki/National_Council_of_American-Soviet_Friendship