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Ugh I KNOW!! He bothers me so much. And I'm kind of a pacifist myself but I told my husband that if he talked to me that way there would be fist to cuffs lol.
Boot the player with the foul RL temper and shipoopy attitude. If you are all adults it shouldn't be too wounding to his view of the world and his place in it. He is probably dealing with some other internal issue and coming at the rest of the world p--- poorly. In the real world if you act like a turd it doesn't matter if you can quote page 221 of the DMG to the group. Even if he is an immediate relative he deserves no special "this guy gets to act the fool" allowance.
If he's going to act like an antisocial 5-year old then maybe he'd respond to a sticker chart? After not being a jerk for long enough he gets a shiney Little Mermaid sticker. When he gets ten stickers he can have his experience points increased to match the average party character level. I do a similar thing with my four year old daughter from time to time and it's amazing how much a sticker can modify human behavoir.
In terms of pacifism as a concept, it's definitely an uphill battle that can end up with little more end-of-the-road reward than you being able to saunter into the nearest nerd saloon and say (in your best John Wayne accent) "Heya barkeep...I played a PILL GRIM for 11 levels once" and then get free drinks. So coming up with a couple other character ideas is probably a good plan.
However, you could come at it from a different angle. Roll up a cleric (with a decent charisma or at least not your dump stat). Play the pacifist for the first few levels as it won't sink the boat as long as you are sticking to healing, buffing, protection from <insert least favorite outsider here>-ing, and the like. Then when you get to be high enough level (I wanna say 4...don't have my materials handy) you snag Leadership. If you ever need to attract a gaggle of followers you could BUT...you are mostly in it for a cohort. Have the cohort be Smashy the HGH fueled fighty character...they are then your main character's body-guard. Thus you maintain your desired concept of no direct violence. Then when the game starts to get more intense in the combat arena (like level 6 or 8...kinda depends on the style of the campaign), you have your body guard to help out in thumping evil toad monsters and you can make sure the party is healthy, plump and protected (which is the secret lot of the cleric ANYWAY). It won't make you an optimized power-house and isn't a "recommended build" but you won't be entirely useless and you get to do something kinda sideways from normal which can be fun.
Heh, I ran a steampunk game using Spycraft a few years ago. In two years of play they got into fights three times! It drove me crazy.
They would talk, charm, trick, and, on one occasion, dance their way out of conflict. (This last involved two partner swaps and some illusions. Three card Monte with people dancing....)
And the person who got into actual fights all three times wasn't the soldier, it was one of the mages, a fencer.
After a while I started thinking of it as the Scooby Punk game - 'It's a mystery gang! Let's go solve it!'
In retrospect it was one of the most entertaining campaigns of my life - and one that produced some of my favorite 'war stories'. But at the time it drove me nuts!
Just remember, Einstein was a pacifist, and he personally endorsed the development of the atomic bomb... Something to think about when developing a "pacifist" character.
