I think it's important to look at the bigger social picture and notice that the demographic for "geeks" will be dominated in large part by single, childless, north American, educated white males between the ages of 18-35.
I think having that group in the majority is what fixes the constraints that produce most of these so-called geek traits.
in reply to Please remember that geeks have their own social mores.
So geeks, as you've described them, are arrogant towards people who are slightly different than themselves, possess an inflated sense of self-importance, and a sense of outrage due to this importance not being recognized by others, take an unnuanced, black and white view of the world and of many matters in which they've had no direct personal experience, and indulge themselves on a narrow range of personal interests and hobbies.
Did I miss anything?
What you seem to be describing is the average teenage male. :)
So this recent phenomenon of "geek" subculture might be better understood as being due to a large segment of the male population remaining immature well into adulthood, which has been acknowledged by a few sociologists and reported in the media.