Absence of evidence is not evidence of absence. This is exactly how science works. One observes, posits a theory and lastly proves it. Theories are a speculation by default
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).
http://www.independent.co.uk/news/world/us-government-pentag...