The best thing I've learned to do is:

Always keep quiet until one of the following conditions are met...
1) If you're winning, talk. Call out incs, give strategies. The team loves you. You'll get flooded with private messages asking how you're doing what you're doing and what program(s) you use, etc.
2) If you're losing, keep quiet. The team may talk about "the multiboxer" but they never talk directly at/to you. Less frustration on your part. Lose your game and re-queue.
3) If your team is losing but they see you taking out groups of 5+ of the opposite faction like it's going out of style, the team will know you're not the failure and they'll complain amongst each other.

If you fuel the flame and feed the trolls, you'll just get into an Internet fistfight and no one wins.

A lot of the flaming is done before the battle starts and people inspect your gear.
--> If you're still gearing up, you'll get some "LOLs" or "oh great, a multiboxer... this is fail".
--> If you're well-geared from the get-go, people either don't say a word or they say "AWESOME WE GOTZ A MULTIBOXER! WIN!"