the internet from the forum perspective is pretty obvious. inside any community vehicle there will be a few select undesireables, as there is no real consequence. it's no mystery that the anonymity of the internet causes people to amplify, exaggerate, or altogether change their persona, because in the end, no real recourse can be taken against them.
i've moderated for a few UBBs in the past, and this happens all the time -- despite the quality of your membership and topic, you will always always always have a few trolls and miscreants. it's the nature of the 'net as it pertains to community discussion groups. if you want a perfect illustration of this, go to any UBB, or hop on USENET or mIRC and check the trolls and antagonists in newsgroups and IRC channels. in "real life," you don't get this behavior because the threat of consequence is immediate.
so despite your patronizing tone that implies you have the internet pegged much more thoroughly than I do, there's my response.