If you take a look at the conspiracy sub on reddit, which became popular after the DNC Scandal, while there is some nonsense, the most-upvoted stuff are often quite interesting. In fact, I find the userbase there in some ways more sane and rational than your typical political online forum, often being even quite the opposite of the identity politics seen in those places, ie the #3 most upvoted post this year is exactly that.(1)
1 - https://www.reddit.com/r/conspiracy/comments/6twr5k/the_only...
I'm confused by this statement. /r/conspiracy has been shown to have been heavily used by Russian bots/trolls to spread propaganda and truly fake news.
Conspiracy theories are the sum total of everything that could be true, so consequently the "theory" parts are a dime a dozen.
you think of you stopped a random person on the street and asked them about MKULTRA, they would know?
The reality of history is that it is filled with page upon page of conspiracy, and IMHO the conspiratorial view of the world is the correct one. Of course that doesn't mean every presented hypothesis is true either, each case must be weighed with the evidence.
That said, the number one issue otherwise intelligent people have with conspiracy theory is the inability to use the inductive logical approach instead of the deductive one. When we don't have evidence due to coverup, etc, inductive logic is the only tool left in many cases. In most of the well thought out criticisms I see its generally due to the fact that so many expect and want the deductive approach and don't even know there is another.
So to answer your main question, people don't listen to conspiracy theorists because: many conspiracy theorists have week rational skills and adopt views without proper scrutiny, various government and corporate shills actively monitor and attack conspiracy forums, and due to the tribal mentality of desiring superiority, and other factors, people dismiss conspiracy because they have been trained to do so.
Of course there is a lot of plain crazy talk in these types of forums, but oh the diamonds in the rough that can be found.
That's just the meta discussion.
Not surprisingly, the mere though of your government kidnapping and torturing innocents or taking part of genocides is deeply traumatizing.
Denial, distrust or anger directed to people exposing terrible facts is to be expected.
(I'm not referring to the US specifically. This patterns of denial seemed to be common under nazism in Germany where a lot of people refused to believe the magnitude of atrocities committed by their government)