I dunno - could it be socio-economic factors?
Maybe it's watching too much american tv or something, but it seems to me that there are plenty of idiotic immature racist asshole *adults* in the U.S. (and elsewhere) too. However, given that the U.S. is a richer nation and pc's are a more accepted form of entertainment, and internet access is more available, maybe these poorer, uneducated people in the U.S. are more likely to play online PC games than poorer, uneducated people elsewhere? Certainly here in Australia, most of the people who are sufficiently nerdlike enough to play an online RPG and have a good PC are probably mostly late high school, uni students, or professionals. The asshole people are all drinking at the pub every night and beating their wives or whatever it is they do, not playing online games.
I'm not suggesting that richer, more educated people are nicer or are better people (I dont believe that and neither should you

, I'm just saying that they tend to self-censor a little more. And I'm saying that, maybe, in the U.S., a greater variety of people play online games and therefore we tend to get exposed to jerks a lot more from there.
Do we have any korean speaking people here? I'd be really interested in what a korean GW forum looks like... do they have the same amount of ranting and raving as the english forums? What sorts of things do they talk about?