The thing is, the guild I'm currently in with my main, is very alt-unfriendly. That's also the reason I dont get to box there, becaues my 'crew' is a bunch of alts. That's why I was looking for a new guild in the first place.

It's not about the fact that they don't understand multi-boxers, I think, because some of them come to my weekly karazhan's and timed ZA events, and they're all loving it.
In my opinion, killing bosses prety much anywhere, with a boxer in the guild, should bring fame to the guild. I'm not quote sure why the people in your guild are leaving, would be weird if it was because of the boxing. In my main's guild, they're all really cool with it that I box, as I said, they just don't want alts in 'main raids'. This might be because they've known me for years before I started boxing though, as I have always been in that guild, since MC and the likes

As for starting an own guild.. I've done that once before boxing, but to be a true successful guild it takes even more time and devotion than multiboxing itself does. I'm not talking about some friend, chat guild that does kara/za, or even SSC/TK. To get to an archimonde/illidan farming state in a new guild takes a while unless its a merge of guilds of some sort.

I just find it so damn annoying that I don't even get a chance to show them the endless possibilities. I've even told all of them that I don't mind if i can only raid once a week, because I take 4 spots, or whatever, aslong as I can raid on my shammies "at all"