It goes back to the "Greater Internet Fuckwad Theory". Take a massive communication net, cheap to get on, and semi-anonymous, you end up with people acting their worst. Admittedly, some people's best isn't much to write home about (or, perhaps you shoud write to their mother...), but once you add username:'anonymous', you end up with behavior approaching to 4chan's /b/ board.

As anonymity on internet approaches 0, respect and sincerity approach in-person communication. And the opposite is true: when perfect anonymity is reached, baseness and vulgarity are the ruling factors.