Last night (Dec 28) TCM showed "A Guy Named Joe". At the end of the movie Osborne noted that the screenplay was by Dalton Trumbo who Osborne said was accused of being a member of the Communist Party and that Trumbo was blacklisted. Dalton Trumbo was a member of the Communist Party. His party card was presented at the HUAC hearings that Ayn Rand testified at. Dalton Trumbo later admitted his membership in the Party.
Trumbo lost his job not just because of his membership but also because the studios had declared that anyone who was guilty of contempt of Congress or using the 5th amendment would not be used by the studio.
Osborne correctly noted that Trumbo used pseudonyms to write movies until 1960 when Kirk Douglas hired Trumbo to write the screenplay for Spartacus
Let me make a final point. No one has a right to be a screen play writer. You have a right to offer your work to others. Movies are a collaborative art.
Ayn Rand has spoken of people who were anti-communists and could not hired by the studios. Even in those rare cases where one person does many tasks his movies are not self-financed.
There would have been no tears shed about if a group of Nazis had been found working in the studios.