I typically get very positive responses to multiboxing...one time I got a hate message from someone only I don't think it was towards multiboxing...

I was sitting in evergrove getting ready to hop a flight to Mok'nathal or whatever, and right before I took the flight someone on my faction says "I hate you and you're a loser".

So in midair I'm like "wtf?" I sent him a whisper saying "thats an awfully strong word to use on someone you don't even know"

To make a long story short he started claiming he knew all sorts of things about me just from seeing me in game, to which I responded "Now what could you possibly know about me other than the fact that I play a female orc shaman in a video game"?

After talking to him a bit more he basically made himself look like an idiot. Asked me what sex I am in real life to which I responded "None of your business" and he basically claimed that since I'm a male playing a female character I'm a loser and he hates me. So it wasn't even a complaint about the fact that I'm multiboxing, AND he had no proof on whether I am male or female. So after he said that I said "Thats all I needed to hear to prove that you're an idiot" and /ignored him

Aside from that I've only ever been harassed by one person in-game - on my own faction. I made a post about it awhile ago but he stole one of my kills and then every time we're in the same zone together he tries to make fun of me in /1, so I ignored him on all of my characters - hes a moron. Cool thing is usually everyone else defends me because I've helped everyone else in the zone against alliance, or helped them kill bosses/quest mobs by having them tag them and then DPSing them down, etc