Learning to live with not knowing things is poor advice in a context where people are actually hiding things from you and what is not known is what the people are hiding rather than whether the people are hiding something.

No, if you can't stand thinking that you don't know how things work you are pretty easy to convince of a lie. You take the first lie that makes a bit of sense in your view of the world. The lie feels like you understand the world. It feels better than uncertainty. Any decent organisation that operates in secret puts out lies to distract people who want to know the truth.

Andy Müller-Maguhn was standing in front of the Chaos Computer Congress in German and managed to give a good description of how the NSA surveils the internet and how the German government lets them spy on German soil. At the time you could have called it a conspiracy theory. Those political Chaos Computer Club people are very aware of what they know and where they are uncertain. That's required if you want to reason clearly about hidden information.

Needless to say, 9/11 and lizard conspiracy theories fall in the first category and the material that has been censored from lesswrong falls in the second category.

When it comes to 9/11 the government does hide things. 9/11 is not an event where all information is readily available. It's pretty clear that names of some Saudi's are hidden. Bin Laden comes from a rich Saudi family and the US wants to keep a good relationship with the Saudi government. I think it's pretty clear that there some information that the US didn't want to have in the 9/11 report because the US doesn't want to damage the relationship with the Saudis.

Various parts of the NSA and CIA do not want to share all their information about what they are doing with Congressional Inquiries. As a result they hide information from the 9/11 commission. The NSA wants to have a lot of stuff out of the public eye that could be find out if a congressional commission would dig around and get full cooperation. The chief of the NSA lied under oath to congress about the US spying program. A congressional commission that would investigate 9/11 fully would want to look at all evidence that they NSA gathered at that point and that's not what the NSA wants, even if the NSA didn't do anything to make 9/11 happen.

If someone finds evidence of the NSA withholding information to a congressional commission that shouldn't surprise you at all, or should increase your belief that the NSA orchestrated 9/11 because they are always hiding stuff.

Information about Al Qaeda support for the Muslim fighters that Nato helped to fight for the independence of Kosovo isn't clear.

The extend to which Chechnya Muslims freedom fighter are financed by the Saudis or Western sources isn't clear. The same goes for Uyghurs.

General information about identities of people who did short selling before 9/11 was hidden because the US government just doesn't release all information about all short selling publically.

The problem with 9/11 is that people go to school and learn that the government is supposed to tell them the truth and not hide things. Then they grow up a bit and are faced with a world where government constantly hides information and lies. Then those people take the evidence that the government hides information in a case like 9/11 as evidence that the US government caused the twin towers to be destroyed with dynamite.

Politically the question whether to take 9/11 as a lesson to cut the money flow to Muslim 'freedom fighters' in Chechnya does matter and it's something where relevant information gets withhold.