There is a particular hazard that comes with being a genuine dissident or whistleblower or an otherwise deeply committed critic of things: to really do it involves demolishing your standard frame of reference. The things that other people go around believing, the assumptions that are supposed to constitute your shared reality—some fundamental part of that structure, you come to understand, is just purely false. The government will lie to you about something as plain as how many people died in an earthquake, and where; what seemed to be your available zone of free expression and disputation was secretly a box that could close on you at any time. And so you have to fall back on your own judgment about everything. You can't trust what you're told. Every condition in the world is up for debate; every apparent fact could be the front for another conspiracy. If Seymour Hersh could catch the government lying about a thing as terrible as My Lai, in front of the whole world, why should he trust the official story about Seth Rich, or about Syria's use of chemical weapons?
Suggest heuristics should differ between how you treat someone acting conventionally and someone acting unconventionally (within some scope). Earned trust relationships for the former. Setting aside how much you might instinctively distrust the latter and evaluating things independently -- and not assigning their later pronouncements more weight because of earlier ones.