I don't play WoW but I do belong to one of the top raid guilds on my server in a different MMORPG. My guild is primarily adults so I generally don't get as much flack for being the token vegan as I might if the guild was more immature but I've had my share of jokes on occasion. I found when someone says anything moronic it's best to let it slide off your back and chalk it up to ignorance.
If it persists and you can't work it out with that individual, I would just put them on ignore. As someone else pointed out, you can't expect to get along with the entire population and some idiot will always come along with a silly remark to ruin your day. The one thing I wouldn't do, however, is get overly defensive and argumentative because people in these sort of situations love to push hot buttons when they find what they perceive to be a sore spot.
On the up side in my situation, I've almost convinced my guild leader to go vegan and I've been able to recommend some good vegan products as alternatives for guild mates who have allergies.
Support your right to arm bears. ~Cleveland Amory