Re: the devil and rock and roll
I think that the most rockers(especially Tremonti) don't actually mean anything satanic by using the sign, it's just a part of their rebellious aditude. Still I think those of them who are christian should be more aware of it's meaning.
I personally also like celtic art and don't see anything satanic in it but I don't use any symbols that I don't understand.
Anyway I don't think classical music could ever be called satanic because it simply has nothing to do with satan so I think there's a big difference between rock(especially metal) and classical music. They might not (all) be believers but you won't see them use \m/ or worship the devil.