One thing I notice is that most of the rudest are anonymous. I also discovered something else. The rudest ones are goons working on behalf of people or movements or, gasp, even other companies, and that they are trying to disrupt things by just being rude.
Here's yet another example: comments destroy blogs and bloggers. When stuff like this breaks out, you keep wanting to tell the trolls: "Get your own blog and write your drivel there!" But they won't -- because your comments supply them a better platform from which to sling mud.