I’d say this describes Reddit much more than Twitter. But in fact it describes humanity, which the social web is simply a reflection of. the root of the problem is the human heart and the lack of empathy, understanding and love (as in philos or agape) towards those who are not like us. Neither Twitter, Reddit, Facebook or any other social network is going to change human hearts — as nice as that would be, because that kind of change comes from within, not from without. Besides, they see their mission as to connect humans and give them a means for communication, not changing their nature.
I know that abuse exists on Twitter from reading about it in the news — usually involving famous people, who will be attacked by someone no matter what medium is used. But I’ve never seen it in my feed EVER — I see plenty of disagreement but it’s quite civil and often informative. So if you feel like you’re in a mosh pit then maybe you need to move to another part of Twitter. By the same token, there are plenty of parts of Reddit I would never go to, but here are also some subs I find informative.
Also, consider that even the abuse that does happen on Twitter, as appalling as it is, represents a big improvement over previous “social web” methods such as stoning and lynching. Humanity still has a long ways to go, but thankfully we’ve also come a long ways.