Buy a new tyre. Seriously. It cannot be removed without cutting the tyre up which defeats the purpose of removing it in the first place.
To be honest, if you use decent sealent (Stan's) and ride those wheels regularly there shouldn't be a problem (becasue the sealant will always get sloshed around pretty evenly that way). But if they are race only wheels then sealant is not really a good idea as they spend most of their time laying around, allowing this sort of thing to happen.