frankly, any evidence besides zero would be good, but ideally any evidence which is convincing. It's up to the conspiracy theorist, not the audience, to come up with such evidence, whatever it may be.

an example of evidence of such a conspiracy theory would be internal emails telling a reporter to go easy on the US government because a small portion of funding comes from it, or to attack X because the US government wants them to

statistical evidence would work too if it proves the claims of bias somehow, I leave it to you to figure out some examples