Yes, that’s exactly my point.
> What you mean is counter-intelligence
No, I do mean McCarthyism. The pitfall that counter-intelligence easily falls into where they end up targeting innocent people rather than actual spies.
A spy spends every waking moment trying to not look like a spy. Gang Chen on the other hand spends every waking moment trying to figure out heat transfer and nothing about not looking like a spy, because he “has nothing to hide”. That alone is going to make him look more like a spy than a real spy.
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.
What you mean is counter-intelligence, and yes, that's absolutely an important thing.