Shame on you, anonymous commenters.

I read Above the Law pretty regularly, and I have to say that I'm saddened by the tenor of the comments overall.  I know that the comments are unmoderated, and I don't blame Above the Law for them (or any blogs that allow anonymous, unmoderated comments).  What I don't understand is the mentality of people who write hurtful, anonymous things about people they don't know (or, for that matter, people they do know).  What is it about anonymous commenting that gives people the license to be so horrible?  (I'm guessing that the commenters have never been on the receiving end of any of the drivel that they're posting.  I have been, and it's an awful experience.)