People with insecurities do the darndest things..
I know nothing about your game, but it still sounds familiar.
All the people I game with come to the table for different reasons.
Somehow, this guy has determined/settled on/been rewarded that this is the reason he comes to the game. How do we convince him that belittling kibitzing and morale breaking is contrary to the reason everyone else shows up?
1) Payback: Doing it to him may not work. These people generally won't look in the mirror and may just foster a free-for-all game killer. And while the rest of the group has expected it from him, you may be judged more harshly because it's out of character for you.
This is up there with passing the GM a note that says "HI" every time the creep does it. If he's not paranoid, he will be.
2) Backup: Have you talked with the GM/other players? I'm sure you guys all know each other pretty well. Who knows if this will help. Never hurts to try. You may not be the only one who doesn't appreciate his attitude.
3) Leverage: Who's house/game-site is it? "So-and-So is being a ***k! I don't have fun and I my MechWarrior stuff is in the car!"
4) Diplomacy: "Are you enjoying the current campaign? Maybe we should team up to accomplish a mutual goal.."
5) Ego Stroking: "You didn't look happy with that last rule call. If you were GM, how would you have handled scenario XYZ?"
The real deep hurt guys may just brush you off. The attention seekers will wax loquacious about their wisdom in past calls. Listen to him out of game. 'Could be all he needs.
6) Cleanse by Fire: Vote him out of the group. Burn his character sheet. You could just let them know that he sucks. Let him know that he sucks. Each time he does his shtick, he's wasting game time. Disrespecting everyone at the table. Good gamers are worth keeping, bad ones can play in other people's games.