It used to be Blood Elves who would be beating you over the head with the DPS stick in randoms and looking for any and all reasons to give you a sermon about how much you suck before they vote kick you and laugh at the 45 minutes of precious life you just wasted in the queue.
But you know, lately I've been seeing much more of this come from Pandaren, notably the female of the species. Go on the official WoW forums and look up some hot topics like CRZ ganking, LFR loot, vote kick abuse, etc. These broads are always the ones filling in the "PvP on a PvP server!", "I'm not carrying you...", and "I would have kicked you too..." elitist post templates.
Now in the past people had surmised that perhaps the male Blood Elf, being tall, slim, and muscular, appealed more to the kind of person who took WoW so seriously that they set out to make sure everybody else knew they were their inferiors every time they logged in. We can only really offer guesses as to why it became the race of choice for all the Henrys (http://www.youtube.com/watch?v=IXUzeMZXNik) that make WoW suck.
For some reason now they've all taken up female Pandaren and this offers us a second chance to get into their heads and figure out why.