the danger isn't in McCarthyism itself; it's the danger that McCarthyists pose to a society when they make accusations that either a) turn out to be false all together or b) were the result of agent misinterpretation or lies for the sake of personal career advancement.

McCarthyists accused and found so many 'red spies' not because they existed (although they did in very limited amounts), but because McCarthyism generated them through false accusation, followed by an unwavering inability to admit wrongdoing or fault.