I just have to say:
When people make claims that you're cheating, I find the best response is a logical, patient one. Usually I just explain I have multiple accounts, and I'm working on mastering to control them with one keyboard. Then they say something about how much money I pay, and I crack a joke about paying more for gas than the 60 per month for 5 toons. Then they almost always ease up and appreciate the lighthearted responses and cheer me later on. Eventually a lot of people on your server start recognizing you and either accept you or admire you. I've had nasty people /yell cheater and stuff, only to eventually accept me when then realize what i'm doing is pretty neat.
In BGs I have a little more tolerance than normal and typically just ignore tells because I'm busy owning stuff up. But even there sometimes I take the time to point them to wowwiki's multiboxing entry, and later on they see me in BGs again and cheer me.
I don't think ignoring clears anything up, I definitely don't think making immature responses to immature remarks makes friends either. Simple friendly responses go a long way in the end.