I never responded to anyone, and I usually had BG chat turned off. Sometimes people would follow me around in a BG and /say or spam emotes, I had a 5x AFK debuff macro - that would always make them leave to get into combat. But, after awhile even that wasn't worth the effort.

There's still too many of these posts: how do you deal and/or win with haters. You don't. You don't deal with them, reason with them...you don't even acknowledge their existence; nothing is worse than being ignored. You're multiboxing for your own reasons, and hopefully none of those are to convince anonymous people online of anything.