As for children, I blame parents who do not properly (for whatever reason) educate them. Children messing up on game servers is just an aspect of the problem, some children just can't socialize in a civil manner because they were raised to believe (or weren't thought otherwise) that the world revolves around them.
There's a myriad of issues that compound to that. It's a common thing for both father and mother to work outside the house, not being able to be around their children as they would like to or as they believe they should. They feel guilty about it and then spoil their children trying to compensate for, relaxing on restrictions they should impose, not punishing them when they do bad things and so forth.
Also, people blindly buy anything written in such "How to educate a child in ten easy steps", just because this or that book happens to be signed by some "doctor" they never heard of before, and who probably never even been near an actual child.
Finally, children are impervious to being educated by society when their parents fail in that. Where I live, school teachers were rendered impotent to try and instill any sense of civility to children. In fact, they have been stripped all powers they once had, even those directly associated with class and education matters, just because every children is, "Oh, so special...", and "God" forbid, anyone but the parents entertaining any voice of authority over them, lest them traumatize the child for life. But wait! Parents have no time to spend educating their children anymore...
This isn't recent, some of the spoiled children from the late eighties, early nineties are adults now and you don't have to look too hard to find them little obnoxious adult-brats. I know a few of them myself. Good thing is that real life does reserve certain harsh lessons that can affect even adults and some people will learn better even despite their upbringing. Some will not.
Along the lines of something George Carlin once said, "Modern society has developed a fetich for children. It's bull**** and it's bad for you."