Firstly, If I'm only only pulling 10k DPS, maybe it's because I just hit 85 yesterday and am new to heroics. Maybe I'm not 'retarded', an 'idiot' or full of “FAIL”; maybe it's more about my gear kinda sucking to hell, which may be the reason that I'm there to begin with. Seriously, maybe you could spend less time thinking up insults and more time thinking 'probabilities' here.
My best guess is that your ridiculing may be a misguided effort to call attention to your own 30k+ dps, which is self-defeating because any kudos you'd get for it go by the wayside while others are occupied with speculating whether or not you have a touch of the Down's Syndrome yourself (or are just 10). Jabbing at people's DPS in instances is like making fun of overweight people while attending a Weight-Watchers meeting, and doing so while wearing a super-fantastic belt of slimming (which they give out for free on your 20th meeting). Some people just aren't there yet, but they're doing what they can to get there. Which makes them less “retarded” and more “doing exactly what they're supposed to be doing”.
So when the insults start flying, the group gets uncomfortable and suddenly what was supposed to be fun has turned sour for everyone. And of course it's awkward...so awkward. Hey sometimes confrontation is inevitable and it's not always pleasant, but to have it stem from someone who's actively avoiding all logic and reasoning in an effort to try and condescend others and/or show off their DPS? Well that's like being horribly disfigured with Leprosy and yelling at people to admire your awesome haircut. You end up just making others wish they could choke your neck a little.
A better way to call attention to your awesome DPS? Say nothing. The strong-silent type is the most awesome of all, IMO. I was in a 25-man raid just today, admiring a DPS who was almost 2 percentage points above the next top DPS and thinking to myself, “Wow...look at that guy go...very nice!”. When the raid ended, he announced that, “Wtf I'm stoned to hell and still 2 points above your guys' dps roflmao!!”, which instantly transformed him from great DPS'er to “Some attention whoring bastard”.
Or, on a somewhat related note, how about the DK tank who's dishing out 40k DPS while you're fumbling around with trying to get off two spells in a row? He's tearing through mobs so fast that you're constantly forced to play 'catch-up' and, oh crap, gotta loot something? Well it just put you that much further behind – you should have just left it. Run to catch up, hopefully cast a spell or two, rinse and repeat etc and find yourself grimacing when the healer's constant pleas for mana are intermittently punctuated with the tank announcing how he's doing almost twice as much damage as everyone else. “Pick it up dudez”.
Well how about you listen up, zippy: since you're the tank, you're going to be the first to every mob and the first to attack. Coupled with your fully gemmed raiding gear, and the fact that you're a frickin' DK, well that's a recipe for you to easily get the most DPS. Plus, you really seem to be striving for it, so yeah, we get it...your DPS is awesome. As well as cliché....I mean, you're a frickin' DK. What'd really be amazing is to see a DK who wasn't at the top of the DPS charts, ya know?
And to be honest, it's not that I dislike Dks....I just don't like playing WoW with them. At the beginning of a run, say “Hi all” and see who responds with “Sup” or “Yo”, it's almost an easier way to quickly identify your DK than mousing over names is. If WoW was a ski resort, Dks would be the snowboarding punk bastards.