This thread propagates the maxim that people will always think of something new to divide and distinguish their-selves from others so long as it establishes a sense of superiority in belonging to the more 'noble' tribe.
My experience has been that the lycra-clad racer type is more likely to be an arrogant so so and so, but that is just because these are the types one often comes across in London; there are plenty of decent cyclists of all ilks. One could find obnoxious persons amongst mountain bikers, and *gasp * even folder fans.
Generally, these arrogant types tend to be those that hold theirselves to be amongst the elite, or the hardcore of their said groups - ie. those with least to offer out-with their desire to be seen as a Platonic form.