I think the unashamedly public display of dorkdom is what makes them the most open to ridicule.
Most other dorks are basement dwellers, or anonymous via the internet. Being out in the open among typical park-dwellers like the dog-walkers and the joggers and the bike-riders, usually in pretty bad costumes, hacking at one another with padded sticks, grants the non-initiated a skewed view into the world and must invariably lead to a later conversation that starts out something along the lines of, “I was at the park walking Rover earlier and saw a bunch of adults with green face paint and fake swords running around like madmen and shouting ‘Fireball!’…”
The people I knew that LARP’d, that tried to get me involved, seemed to be more of the opinion that the entire thing was set up so that people could beat one another with sticks. Their costumes were pitiful, their weapons and armor laughable, and the rules (as I read them) seemed entirely biased towards spellcasters.
Essentially, what I gathered (and this was just this group, though they did belong to a nationwide organization who had a whole “book” of rules), was that anyone with a quick wrist and decent aim with a beanbag ruled all. After that, regardless of class or level, being better at handling a sword gave you a huge advantage to someone who wasn’t as good.