from my experience people on the "normal" part of the internet don't act like douchebags at all, in fact they act way too nice as if they're scared of someone feeling hurt, however they will become worse than hyenas when someone is "exposed" (e.g.: someone says something racist = violence is ok)
as for nu4channers they get to know 4chan through media that paints it as the secret hacker club where everyone is racist so if they intend to stay they will spout all the worst crap they can to fit in, i know this from experience because i went through it
it's really sad to see, sometimes it's painfully obvious when someone is trying too hard to fit in