Everything I've learned about the cold war and McCarthyism is about the dangers of a witch Hunt (and it's frequently combined with The Crucible to make the point). The problem with this is witches don't exist, communism is at least a reality in the world. Was communism an actual threat in America, and how much? Thanks!!
If you subscribe to the thinking that communism and capitalism cannot coexist, then sure, communism was a threat to America. Especially given that the countries main competitor at that time, The Soviet Union, was communist. However you could also argue that in a Democracy people should have the freedom to be Communist and vote Communist if they choose and that one could be Communist without supporting the Soviet Union.
However, the vast majority of those accused/blacklisted were not Communists and only rarely associated with the Soviet Communist party. The vast majority were left leaning liberals, thus the witch hunt comparisons. It became more of a hunt for anybody in the public light seen as "left-leaning" than anything else.
So "witch hunt" might not be a perfect metaphor, but it's pretty darn close.