The article A Group Is Its Own Worst Enemy (
http://www.shirky.com/writings/herecomeseverybody/group_enem... ) gets into that a bit.
One of the interesting bits in there is:
> The second basic pattern that Bion detailed: The identification and vilification of external enemies. This is a very common pattern. Anyone who was around the Open Source movement in the mid-Nineties could see this all the time. If you cared about Linux on the desktop, there was a big list of jobs to do. But you could always instead get a conversation going about Microsoft and Bill Gates. And people would start bleeding from their ears, they would get so mad.
Which can be seen in Stack Overflow (its the newbies that don't read that are messing everything up) and reddit (Stack Overflow aka Downvote and Duplicate). Each group is making their group stronger and a more firmer identification by vilifying the other group (merited or not).
This happens in all groups.
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The "everyone is mean" nature of some of the communities, I believe, comes from further down in the 'three things to accept':
> 2.) The second thing you have to accept: Members are different than users. A pattern will arise in which there is some group of users that cares more than average about the integrity and success of the group as a whole. And that becomes your core group, Art Kleiner's phrase for "the group within the group that matters most."
> The core group on Communitree was undifferentiated from the group of random users that came in. They were separate in their own minds, because they knew what they wanted to do, but they couldn't defend themselves against the other users. But in all successful online communities that I've looked at, a core group arises that cares about and gardens effectively. Gardens the environment, to keep it growing, to keep it healthy.
> Now, the software does not always allow the core group to express itself, which is why I say you have to accept this. Because if the software doesn't allow the core group to express itself, it will invent new ways of doing so.
When the core group lacks the tools necessary to maintain the vision / success of the site as a whole, they are going to find other ways to defend themselves from excessive workload. The easiest way is to be rude to people so they go away (and the overall workload is reduced).
I believe that this pairs with the (misguided?) efforts of Stack Overflow to become more inclusive by lowering barriers to participate (see design for #3) and making it harder for the core group to moderate content (be nice, changing close reasons, removing 10k rep flagging assistance, reducing 15k rep protection ability, a diamond moderator culture of "if it got upvoted it shouldn't be deleted unless there's vote fraud").
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The entire article is a very interesting read. The author's credentials is also an interesting read - https://www.bloomberg.com/research//stocks/private/person.as... . Check what organizations he's a member of the board at.