Re “McCarthyism” one of Hollywood’s many dirty secrets is that there never was a blacklist even though they still whine about it six decades later. The so-called Hollywood 10 just kept working under pseudonyms for a few years, then began using their real names again.
The House Un-American Committee was formed in 1938 and ran until 1975 was the one that investigated Hollywood. McCarthy did not serve on that committee nor did he testify before it.