It's a conspiracy!
No real historian would deny that conspiracies have happened in the past. The history books are filled with examples. You can even find many examples of people in foreign governments being participants in conspiracies.
So, really, the only objection that "rational people" can make against current conspiracy theories is that they simply can't accept that people who are involved in the US government could also be a part of a conspiracy. This is unrealistic and delusional.