"......The crucial difference between having a preconceived notion — we all do that, of course — and conspiratorial thinking is when you get into that self-sealing reasoning and ignore every piece of evidence that is pointing the other way, when you’re starting to broaden the circle of conspirators, and when your skepticism gets to be nihilistic — when you believe absolutely nothing that the government or the media is saying — that’s when you’ve crossed the line...."<quoted text>
Actually it is the government that comes up with the conspiracy theory, like on 9/11.
The book "9/11 omissions and distortions" is about what facts the 9/11 commission considered and those that they decided to leave out.
So picture a jury getting to see certain evidence but not allowed to consider certain other evidence.
A different verdict can conclude when evidence is withheld.
So many conspiracy theorists point out facts that were not considered. by the commission.
Plus the commission started with a conclusion and worked back to the beginning, instead of start to finish and a conclusion based on evidence.