Black mages are never really had bad guys, they just wield a destructive power as appose to White magic where its more of a healing force. One FF I am playing though IV on the DS has them all in a study group. I am not huge on XIV's lore or anything but as I see it, they would just be another school of magic much like in Elder scrolls, yes there are bad magics but we as players can pick if we want to take them or not.
