One of the constant bleats from the political left in America is that anyone questioning the patriotism or motives of the Left is engaging in McCarthyism, a politically motivated witch hunt.
It’s amazing that this has become an effective deflection from legitimate criticism, as McCarthy was right- the government, under the Democratic administrations of FDR and Truman was absolutely riddled with agents of the Soviet Union.
I would urge the reader to study two subjects on this matter- The Venona Project, and the Vassiliev notebooks. Of the two, the Vassiliev notebooks are probably the least trustworthy, mainly because they are uncorroborated. Still, they’re generally in line with Venona, and the prosecution of various Soviet agents throughout the Cold War. Which, by the by, was a long, long list.