Over the years he wrote film reviews for The Kansas City Star, Esquire, and The Hollywood Reporter.
He was an ardent anti-Communist, who contributed to the Hollywood blacklist by testifying against others in the film industry for the 1947 House Un-American Activities Committee.
[5] The play was also produced on Broadway at the Adelphi Theatre from October 26, 1936 to January 1937, staged by Vincent Sherman.
[2] He wrote the script for Paramount's 1939 melodrama Our Leading Citizen, about industrial action, that was critical of both the "greedy capitalists" and the striking workers.
In 1939 he chaired House Un-American Activities Committee (HUAC)'s hearings on the Federal Theater Project.
Moffitt appeared as a "friendly" witness, along with MGM producer and story editor James K. McGuinness.
[1] At first reluctant to do so, he later testified at the October public hearings, blaming filmmakers Frank Tuttle, Herbert Biberman, Donald Ogden Stewart, and John Howard Lawson for "luring him into joining" the Hollywood Anti-Nazi League in 1937.