In the same vein, until I see actual evidence (and not just "Mr. SoAndSo said so-and-so is true), I'll factor in the claims of the US government and media as just hypotheses.

I think its unfair to say that we should refrain from discussing or theorizing about topics when the truth is murky just because we can't test it. I'd test it if I could, but the reality is that we're never going to have that ability (unless we magically achieve complete governmental transparency somehow).