The existence of a highly elaborate, complex, multi-level international Communist conspiracy, despite the glib and smug sarcasm from liberals about McCarthyism, the John Birch Society, or VAST RIGHT-WING Wackos, as a matter of history, is not a "theory" but based on hard facts. The KGB archives, since the Berlin Wall came crashing down, have actually made Sen. McCarthy's claims seem rather mild and understated. There were a lot more than 100 or 200 Commie agents in other words. Just because McCarthy didn't have the evidence to back his claims does not mean they weren't there. KGB penetration was vast and deep.
The Dodd claims seem sensationalist, but then the USSR was a pretty weird monster. The whole Kim Philby psychodrama with moles in British Intelligence was a pretty bizarre episode. Check out the materials on the various mole hunts. Peter Wright's Spycatcher is an interesting read. The stuff on the investigations of the assassination attempt on John Paul II in '81, the death of Pope John Paul I, and all the weird banking scandals in Italy reveals quite a lot on the political and espionage levels focused on the Vatican by various countries. There's no way anyone could read about Hungary in the 1950s and come away from that not understanding that the Catholic Church was a target of Communist aggression and mischief of great interest to the KGB.