Judy Holliday was brilliant. She was a smart and funny, a member of a Village improv group called the Revuers. She was committed to a wide range of political causes, including serving on the radical Voice of Freedom Committee along with Dorothy Parker and Paul Robeson, and supporting the Civil Rights Congress. When she was listed in Red Channels in June 1950, the film Born Yesterday, written by Garson Kanin (also listed in Red Channels), was set to be released later that year, this double blacklisting threatened not only her career, but the careers and reputations of all those associated with the film.
That was the point.
In a recent article titled "This Actress Played Her Famous 'Dumb Blonde' Character to Beat Communist Allegations," writer Jacob Slankard describes how Holliday "adroitly" played her Billie Dawn role from Born Yesterday in order to confuse the interrogators on the House Un-American Activities Committee. But this wasn't an act of moxie: it was an act of desperation. Like others who had been blacklisted, Holliday had hired one of the men who had published Red Channels to help her clear her name. Known as the "smear-and-clear" business by those subjected to it, American Business Consultants (the group behind the blacklisting newsletter CounterAttack and Red Channels), first smeared people's names in the pages of it publications and then offered their service to the blacklisted (for a fee, of course) to help them salvage their career. It's hard to imagine how humiliating this must have been to those who were blacklisted.
It's also worth mentioning that it's not clear that Holliday wanted "to beat communist allegations," whatever that anti-communist canard means. Her father was a prominent Socialist party member, she worked closely with many artists, actors, writers, and producers who had been influenced by the Communist Party-inspired cultural front, and she continued to defend the rights of those who held Communist points-of-view.