Actually, the initials of the "Federal Security Division" are "FSD", not "SD", so there's no problem (unless of course the Nazis had a bureau known as "Fuhrer Sicherheitsdienst").
As for the unfortunately named Super Dreadnoughts (SD), I suggest redesignating the class as "Honkin' Big Mothers" or HBM. These initials may have problems of their own, but at least they shouldn't be Nazi-related.