If you were a Chinese spy, why would you play the game of releasing the information to the public at all? You'd just go straight to the Chinese and disappear into their protection. There's nothing to be gained by an elaborate charade as a whistleblower.
A damning allegation with global economic consequences is easily dismissed as propaganda if it comes from the Chinese government. Not so if it comes from a whistleblower.
So NSA hired a Chinese spy and didn't know it?
Well, his revelations about the extent of US spying in China/HK certainly helps take the focus off of how much cyber-spying China does on the US.
Of course, if you were an American spy and wanted to discredit him, this is exactly what you would say.
We can do this all day...
But that's taking the second derivative of the situation. Most people can barely take the first.
The point is that it's a ridiculous nonsense statement. It can be applied to anyone about anything. I have no problem with someone believing he's a spy based on evidence or even intuition. I do have a problem with a tautology being used as evidence, or to sway opinion.
If the person is trying to deceive you they will attempt to deceive you. Well, duh.