McCarthy's problem was being a daft c_nt on a power trip, with no idea how to actually deal with spies, and heavily based on violating supposed american freedom of thought and association. It was absolutely a witch hunt.

There's in fact no record he ever disrupted any actual spy work, as far as I know, and his legacy is that even in Warsaw Pact he became famous - famous enough to require redefining in popular vernacular "useful idiot" to include him and his supporters.