The HUAC was a committee of the House of Representatives, which existed from 1938 to 1969. Senator Joseph McCarthy was a member of the Senate, where he sat from 1944 to 1957.
He never had anything to do with HUAC or the Hollywood witch-hunt, but from 1953 to 1955 was chairman of the quite separate Senate Government Operations Committee, which was mainly concerned with alleged Communist infiltration of the government, especially the State Department and the Army.
And to say that it was "revealed last year" that George Orwell "passed on to M15 contacts" names of "acquaintances who he considered to be Soviet fellow-travellers" is to betray similar ignorance of Orwell's biography.
It was revealed in 1991 and again in 1996, and fully documented in 1998, that Orwell told a friend in the Information Research Department of the Foreign office in 1949 both about people who might be approached to write propaganda material during the Cold War and also about other people "who should not be trusted as propagandists" because of their known political views. (See The Complete Works of George Orwell, Appendices 9 and 14, Volume 20.)
There was no question of anyone being damaged in any way.