I think it's all three of the things you said, Ray. Lot's of people nowadays just like to argue for the sake of arguing. They haven't much in the way of social graces and lack the thought of how others feel or see how they truly are. Many know they can hide behind the screen and say whatever they please.
I've seen it on other sites as well and then they hold a childish grudge against that person and they don't even know them in life. Stupidity and immaturity.