One of the reasons I generally like HN so much is because there is so much expertise around that the comments often get right to the actual heart of an issue.
A great example is something like the P ≠ NP attempted proof from a couple years back: https://news.ycombinator.com/item?id=1585850 The top comment is extremely informative, nearly the best commentary you could find about the issue anywhere.
Imagine if the top comment was instead from one of the numerous people who believed they had already proved P = NP or P ≠ NP, and they went off about their own theories and disparaged all of the mathematical community for ignoring them. A mathematical quack, basically.
The people who actually understand math could spend their time refuting this guy, but by doing so the overall signal-to-noise ratio of the site would go down, and with it the overall comment quality. And besides, the quack has probably heard it all before and it didn't change his mind. So instead people vote stuff like this down so that the top comments are from people who actually know what they are talking about.
The problem with stories like this is that the equivalent of these mathematical quacks get voted up to the top. The natural hacker distrust for authority, which on one hand motivates good and productive work on privacy/anonymizing technologies, in this case motivates people to post comments that involve low-quality grandstanding and statements about the political situation that are objectively false. Sure it is possible to refute them, but S/N ratio is still lowered and no one's mind gets changed anyway.
By the way, I'm not someone who is downplaying the significance of Snowden's revelations. I just want to read a discussion that really cuts to the heart of the issues, instead of generic outrage, vague calls to action, and outright inaccurate statements like calling the US a police state.