So why the heck do people post them?
e: I care not for your downvote! Posts like the parent kind of ruin HN for me, so if my opinion is so out of the new norm here I'll know to just stop reading it. :)
1. You want to make sure everyone in a community is persuaded of some fact.
2. But you don't want to expend unneeded effort in producing evidence to convince them if nobody needs convincing.
3. So you assert your conclusion as a bald statement.
4a. If anyone denies it, then you know there's a point in expending effort.
4b. ...or, maybe you'll just wait and hope that someone else gets annoyed with the denial and expends that effort for you.
Either way, you've increased the probability that your point will be made. The second strategy (#4b) is likely pursued more often than the first (#4a), because given a saturated community of "vigilant believers", the likelihood of the denial being fought will be nearly the same with or without you--and the cost will be much lower without you. I imagine these people write these as "drive-by" comments, not looking at the results, but feeling smug knowing that they've sicced their in-group on any vocal proponents of their associated out-group.
I think in cases like this, the urge is just to show off -- to show that they're not one of the "sheeple". The poster certainly knows that the POV they expressed is already very common on HN.
It's not even that I really disagree with the claims. But this was an interesting article, and there are so many more relevant things to discuss!
>prisons are overcrowded
http://en.wikipedia.org/wiki/United_States_incarceration_rat...
>the media tells us the world is becoming more dangerous every second
http://en.wikipedia.org/wiki/Mean_world_syndrome
>local police need SWAT teams and assault rifles
http://www.businessinsider.com/the-militarization-of-america...