Contact support and ask, but really just start new guild not like you lose anything if you leave. mailto:support@rovio.com
U lose all your guild mates and it's hard to track them all down. It's the team that makes the guild. And for me at least, my guild mates are usually the best part of the games.
Again you post new guild name it will be in chat if the guild mates that want to leave they will find new guild in search with info in chat box if they don't join and stay guess they don't mind inactive Capt. If it's a problem to all they will join if they do like the guild. And not hard to track guild mates down if they all on forum or guild prvt forum . Anyways contact support they Will say no way to, but ask.
I had the same issue. I just messaged everyone for a few days and started my own group. Worked no problem.
Mmmmmmmm Tron, I FIND YOU AGAIN ON THREADS ABOUT REPLACING CAPTAINS!!!!!!!! BACK TO THE SHIP AND GET PLUNDERING YOU DOG, IM YOUR CAPTAIN AND YOU BETTER GET USED TO IT
AtariGeneration was formed in the same way. When I first joined a guild it was to learn the mechanics of the game more. After a week in a guild with 30 members and only 7 messages, I decided to leave. I highly recommend this and you'll see a lot of active members leave for an active guild.