Government is way too incompetent to pull any of these crazy scenarios off....
Especially while keeping it quiet.
Look at the big government scandals of the last few decades, how many people were involved and how they were outed. Then line them up against common conspiracy theories and look at how many people would have to have been involved in them and how perfectly they would have to be executed and how many people would have to be kept quiet. Any rational analysis will quickly conclude that a government that couldn't keep a blow job in the oval office secret, or a hotel room wiretap, or low-key, small-scale sale of arms to Iraq, or prisoner abuse in a prison on the other side of the world, could never manage what the conspiracy theorists claim.
And, actually, this isn't even evidence of incompetence. Keeping secrets is really hard, and it's darned near impossible when the secrets carry moral baggage that encourages disclosure. Someone eventually outs it. Attempts to bully or eliminate possible leakers to keep them quiet just generates even more secrets with even more moral baggage. In North Korea, Kim Jong Il can probably suppress information he wants suppressed. Most of the time. In the US? No way.