I sometimes wonder if both the McCarthy-ite HUAC fiasco and the entire Cold War, with its red scares, weren't political moves designed to demonise socialism and communism in the US, and take away their domestic political influence - which was significant, at least until the 1950s.
McCarthy was more than a little bit a mental case and brittle to boot. Nixon famously had his paranoid streak but had much greater resilience. Both were supported by Republican reactionaries who wanted to roll back the New Deal--and who now have largely succeeded. As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."