I only look down on single-boxers.

(kidding!)

I dual-boxed in Everquest, I've dual-boxed in City of Heroes, I've dual/triple/five-boxed in WoW. To be honest, the idea of looking down on someone for boxing 2/3/4 characters instead of 5 never occurred to me. That's like a hardcore raider looking down on casual players. It's not an issue of good/bad or right/wrong.