I think programmers helping each other on Stackoverflow is an example of people being nice by helping each other. It's possible to create any kind of social norm in an online community.
Often the problem is that there's often no moderation that enforces any community norms. Most newspapers don't invest the necessary resources that would be required to get decently moderated comment threads.
You're referring to the problem with people being mean to each other within a given online community. I'm thinking more of people hating each other more in real life because the Internet lets them seek out unfiltered outrage from people with similar beliefs, with nothing tempered by gatekeepers as in the days before the Internet and the rise of cable news.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.