Senator Joseph McCarthy, was arguably, one of the most successful conspiracy theorist in American history. McCarthy was able to meticulously manipulate the Red Scare hysteria with the help of the media, the encouragement from the Republican Party, and this enabled him to pursue his agenda of combating the supposed red infestation in the State Department. Communist witch-hunts had become synonymous with the rhetoric of the period.
McCarthyism, was indeed, an opportunity for Soviet propagandists to exploit. McCarthy gave Europeans, who resented American power, a respectable reason for expressing their hostility. You just have to look at the sheer extent of the anxiety and hysteria that developed in American society. The level of blacklisting, denial of civil liberties, the witch-hunts, persecution of American citizens and the recklessness of McCarthy and his demagoguing. Many began to doubt if the country of McCarthy was a safe guardian of nuclear weapons.
He targeted the state department and the army (to his own detriment) and the House of Un-American Activities Committee (HUAC) targeted Hollywood and business organizations in an attempt to root out communists. His methods were largely counter-productive and very destructive. Anybody that pled the Fifth Amendment were immediately interpreted as an admission of guilt. I think it was similar to that folklore hysteria you hear about – reporting your hated neighbor to the police for communist activities or suspicion, and a swat team storms in and grabs them.
McCarthy did not uncover any real Soviet spies, and he was not successful in his efforts – quite the opposite. He went on an anti-communist crusade, which led to the loss of jobs for countless hundreds, destroying businesses, exacerbated Red Scare fears and left an aftermath of uncertainty and anxiety in American society.