I have been participating in various discussion forums for over a decade. In that time I have witnessed the ebb and flow of membership, and the changing moods of the content. Add to that the "Net persona" factor of being able to "be" someone in words what you are not in flesh and blood, and we have a volatile mix. I am left in no doubt that the tone of forums changes along with the environment in which we find ourselves, wherever in the world that might be.
Bernard touches on this earlier . . . We live in a time when the trials and tribulations of the entire world are laid before us every minute of the day by satellite television and Net feeds. We are exposed to daily breaking news which previously would have passed us by, or at least have been old or second-hand news by the time it had reached us. Sadly, good news does not make good news, so we are bombarded with bad, or at least negative news. The politics, finances, environmental, and social woes (both ours, and everyone elses in the world) are laid on our television, radio, Net and dinner table doorsteps.
The whole international and domestic mood becomes tense, with people becoming concerned for themselves, their families, their countries, and even their world. We are all affected in different ways, some more than others, but we are all affected nonetheless. This is reflected in our relationships with others, and that includes those we have on the Net. I believe the instances of aggession we see flaring up on discussion forums is an insight into the levels of pent up tension, frustration, and aggession in society as a whole.