Trying to scan through the unread newspaper that has piled up in my office today, I came across an interesting article on October 1 in the 
Wall Street Journal on uncivil and aggressive behavior online.  Here are some of the points raised:
- Anonymity is a powerful force.  Hiding behind a fake screen name makes us feel invincible, as well as invisible.
- Most of us present an enhanced image of ourselves online.  This boosts our self-esteem.  And when we have an inflated sense of self, we tend to exhibit poor self-control.  Wanting to protect that enhanced view might be why people are lashing out so strongly at others who do not share their opinions.
- We are less inhibited online because we don't have to see the reaction of the people we're addressing.
- Because it's harder to see and focus on what we have in common, we tend to dehumanize each other.