It's true. Folks should look up the Venona Project and the decrypted intercepts from that era. Far beyond Hall and Sachs spying at Los Alamos, there were indeed many spies throughout the government (it was the height of the Cold War, after all).

Similarly, although Nixon was famously paranoid, he was also right about the soviets fomenting and amplifying vietnam war discord, too.

If they are on here, is that the communists infiltrating the capitalists or the capitalists infiltrating the communists?