i believe that this is called internet asperger syndrome. (please correct me if i am wrong here)
the idea is that with anonymity in position, people are free to act how they want, blame it on something like asperger syndrome, and no one is able to say "you do not have asperger syndrome, you are just an idiot" because everyone is anonymous. thus, you cant tell.
i am usually bland enough to be unphased by most insults from people online. it just does not affect me that someone who i do not know thinks i am whatever they tell me i am. and if i answer, it is a cold answer, no anger, but an air of disappointment that seems to diffuse most people.