They're so easy to irritate and they hate being laughed at.
Personally? I started reading DU because I couldn't believe Americans were saying the things being said there, and since I've always been around normal Democrats it really was a shock. People at DU have no idea what normal Democrats feel and say about them because they isolate themselves in their own little world, they want to suppress views that are different from theirs. They're not the norm at all.
Thats the one problem with the internet - Every village has an idiot, and left to their own means, they do what idiots do and are either ignored or laughed at..However, the internet has created a simple way for village idiots worldwide to find each other, and multiply their idiocy by combining forces.
We have OWS in large part because of the internet -- large parks where village idiots from all walks of life are congregating, copulating, and masturbating like a bunch of primates at the local zoo.