During the McCarthy era, hundreds of Americans were accused of being communists or communist sympathizers and became the subject of aggressive investigations and questioning before government or private industry panels, committees and agencies. The primary targets of such suspicions were government employees, those in the entertainment industry, educators and labor union activists. Suspicions were often given credence despite inconclusive or questionable evidence, and the level of threat posed by a person's real or supposed leftist associations or beliefs was sometimes exaggerated. Many people suffered loss of employment or destruction of their careers; some even suffered imprisonment.

Also:

https://en.m.wikipedia.org/wiki/House_Un-American_Activities_Committee

https://m.imdb.com/title/tt3203606/

They would force people to 'name names' to avoid prison sentences. So everyone was accusing each other of being a communist. Like a witch hunt.