Some of them actually were, or at least had been

Writer James McNeish is calling for an apology to New Zealanders who had their careers destroyed by McCarthyism (audio link). He does a very good job of talking about the unfairness of the process, and how people's lives were destroyed.

His emphasis, in every case he talks about, is how false and unfounded the accusations were, which is missing a rather important point. A lot of the people whose lives were destroyed by McCarthyism were communists, they suffered just as much as people for whom the accusations were unfounded.

Defending only those for whom the accusations were false is actually continuing McCarthyism.