At the considerable risk of taking this seriously……
Alexander Hamilton* reminded us “that men are ambitious, vindictive, and rapacious”. Not a lot’s changed since 1787.
What I mean is, people just are nasty. Not all people, and not all the time, but enough of them, enough of the time. If people can get away with things, they will; here in cyberspace, no-one really knows who you are, and you can say the most outrageous things without fear of consequence.
People often claim that they’re just larking about, that they don’t really believe what they’re saying, and that in real life they’re a pussycat rather than the spiteful individual they appear to be online. I tend to the opposite view; people express themselves more fully online because many of the normal social contraints are removed – Lord On-Line Of The Flies, if you will. I appreciate that this is a very cynical view of the world, but I’ve seen so many examples of “nice” people behaving badly that I assume the worst of everyone until proved otherwise.
*In the Federalist Papers. Who said that an A Level in Political Science was no use, eh?