I hop in this heroic, one of the undead troll ones from Zul'Drak (does anyone really care what they're called?), and the tank asks us to hold up while she makes bolts of cloth for bag space.
The mage is like "Why? No epics drop in here." Like the tank doesn't need bag space because the instance is crap.
The tank ignores him and, once she's done, pulls whole rooms. We wipe in the third(ish) room because a mob found the healer.
The mage prods the healer for not moving away from the mob after he rooted it with frost nova, but he doesn't say it that way. He just says "You should have moved" and prompts irritated explanations from the healer before mentioning the frost nova. Soon, he says: "Whatever. Let's keep going."
I'm rolling my eyes at this point and hoping the rest of the run goes quietly, but after we rez and pull another room the mage links his DPS meter (making me remember that great WoW Insider mage post about how only "jerkwads" link DPS meters in party chat) and starts making fun of our DK.
I've had enough, so I say "Stuff is dying. I don't care."
He promptly makes fun of "the rogue who can't break 2k" and I inform him that he's already fussed at the tank and healer and now he's going after the dps, and he should just cut it out.
He says we can kick him, but then who will kill things for us?
I say "I'm not averse to kicking, but I'm not going to just because you annoy me." (Meaning I'd vote yes if someone else wanted to kick him, but I wouldn't start it myself.)
We're at a boss, so he (thank God) stops talking and stays silent for the rest of the instance, after which he just seems jubilant and thanks everyone. I have no clue if he took my "I'm not going to kick you" remark as winning the argument or if he realized everyone in the group might very well have a good reason to vote "yes, please kick this loudmouth" if I set up a vote, but somehow he figured shutting up was the way to go.
And that's all I wanted.