I have a theory... we all get our kicks from some kind of adrenaline... be it on a bike, at a football match, in the cinema~ historically people attended church for the excitement of the preachers passionate sermon.
At the end of the day, we as mountain bikers, pursue adrenaline and excitement through a positive and progressive medium.
Guys join the EDL for similar thrills via adrenaline, but their path is negative.
Whether this is to do with braincells, upbringing or indoctrination, who knows, but it does kind of suck.
My cunning theory would also tie in with the lack of females, as testosterone and adrenaline are more abundant in blokes.