I think this is a property of the way voting/distribution work on some sites, but not others. On Twitter or Tumblr, if you want to reply to something, you have to increase its visibility in the process. So if something is really wrong and everyone wants to correct it, it creates these horrible positive-feedback spirals where mass-outrage explodes out of nothing. This doesn't happen on Hacker News, partly because the churn of top-level posts cuts off discussions before they can go too far off the rails, and partly because there's a downvote button which makes things less visible. So people reading comments see mostly positive examples (things that were upvoted), which influences the culture, which in turn makes the comments they write better.

Which is not to say that there's no outrage here. But it tends to be a better sort of outrage, expressed by providing context and explaining what's wrong and what ought to be done.