Don't buy it. I was into that kind of stuff when I was younger, and it was a great lesson in human self-deception. Inevitably, these theories rely on you to hang up your hat of rationality and just embrace the wildest claims to validate the 'global-conspiracy' world-view. In order to accept the Secret Space program and all that bunk, you need to believe these whistle-blowers when they tell you that the Nazis never lost the war and that they have a space fleet too, that FTL flight is possible and that FTL is possible because the government is covering up a top-secret highly efficient power-source and engines. These technolgies are based on exotic and non-Standard physics which inevitably will lead you to Electric Universe theory to explain how they operate. Add some aliens and ancient civilizations in there and you're all set. Down the rabbit hole you go. It actually sounds a lot cooler then it really is.
Don't get me wrong, something broadly similar could
happen. Researcher Richard Dolan
once famously said, "There is a secret Space Program. What do you think government satellites are?". I agree with him, an he is a good author to follow if you're further interested in such things, even though he is still a UFOlogist. His books are interesting and well-written, but they are still more or less unscientific.
I believe the non-Terrestrial officers reference you made is that story about the British hacker Gary McKinnon? An interesting story, but at the end that is all it is. One simply cannot believe that he saw secret NASA files depicting UFOs and a military program alluding to a space program without proof, and he has none. Maybe he really saw something like that, or maybe he is a liar trying to weasel out of a harsh sentence by making a scene.
So bullet point here that I do think something similar could
exist (after all, the Soviet space program during the Space Race was pretty secretive - that just doesn't apply to the modern world though), I just don't think that does, and it isn't what is being 'exposed' here online. If the SSP is so pervasive, it should be to easy for citizens to find out the truth with our new-fangled telescopes, panoramic cameras and satellite imagery, thus defeating the point of a 'secret'. The more excuses you make for our ignorance then the more extraordinary the cover-up needs to be.
Furthermore, there is no secrecy in space. Every engine-burn, electric pulse and computer-operation releases radiation, usually infrared. Almost all of the technology and craft that these 'whistleblowers' claim exist would leak some sort of radiation heat that radio-telescopes and other ground-based sensors could detect. So the idea of a 'Secret' Space Program is laughable. The only reason it could have worked back in the fifties is because we didn't have that sort of infrastructure.
Last but not least, I'm really amused when the conspiracy theorists say that our world will turn into a utopia free of government control when we get the secret technologies for the public. These people are obviously not as familiar with corporations and governments as they think they are, because I can guarantee you that there will still be such societal entities in existence if fusion power or whatever pulls through. The infomatrix of domination
(<- that is a real sociological term, not a conspiracy buzzword) will still be in place, regardless of consumer energy-source.