Opponents of the conspiracy theory argue that if a conspiracy truly exists, someone would have said something by now. Let's hypothesize a scenario where that might have happened.
Say some employee of NASA who knows the truth retires. He decides to blow the lid off the conspiracy. He contacts CNN, MSNBC, Reuters, and FoxNews. He tells them that the earth is actually flat and the government has been lying to us!
Wow! Big news, right? Wall-to-wall coverage?
Isn't it more likely that our hypothetical employee would be treated as a crackpot conspiracy theorist and never even be mentioned in the news, or to the public at large?
Of course! Then when this poor fellow just disappears a month later, it's not paid any mind. Why would it be? Nobody is going to believe that the earth is flat. The conspiracy has made damn sure of that.
Who knows how many people have tried to blow the lid off the conspiracy, failed, and paid the ultimate price for trying?
And then of course the leaders of the conspiracy can bring this point up to anybody who needs to find out the truth, adding a new level of threat to anybody who would dare try!
Terrible logic. If the former conspirator worked for NASA, he'd probably be smart enough to show some evidence, like financial records of bribes or video footage revealing a flat earth. Sure, most people probably would think he was crazy anyway, but how do you know that no major news station would even pay a shred of attention to him?
News stations have covered alien stories, UFO stories, etc. What makes you think they wouldn't dso a special on it?
Exactly. Fox aired a special on whether or not NASA lied about going to the moon. Scholars and scientists everywhere were disgusted by the lack of evidence or science to back it up, but Fox hardly cared, because it made money for them. There would be no way that the conspiracy would be able to "lean" on the media to try and get them to ignore it.
As for the idea of the conspiracy using force to back themselves up, this contradicts the earlier argument of "ignoring". Some on this website argue that the government doesn't shut us down because that would cast suspicion on them. Yet almost no one in the public at large has heard of us, so they would run very little risk if they took us out. But they don't.
By the same logic, I doubt the conspiracy would be that desperate as to kill someone that nobody listens to or believes in. To complicate matters even more, what if the rat didn't fade away, as you predict, but actually became somewhat famous for his wild beliefs? Take Bart Stribel, for instance. He never stops popping onto TV to present a horrible documentary. Nobody listens to him, but if he suddenly died under strange circumstances, a lot of people might become very suspicious...
To top it off, Stribel only has "outside" knowledge. Our hypothetical rat, being a former conspirator, might well have some evidence to support his claims.