metal isnt supposed to care about offending people, whether its nazi related, satanic, or just brutally discomforting.
as for nazis, history is history, and turning history into song should not offend anyone.
look at Sabaton, they are from sweden (sweden got bent over by the nazis and you dont speak of it if you go there) yet sabaton sings about all sides of ww2 and their exploits.
primo victoria is about the allies landing at d-day kicking ass, then ghost division is about rommel and the 7th panzer division kicking ass, and the metal community of sweden loves sabaton still.
metal can touch things any other genre cant, its bold like that. the world still understands nazis were bad, but they agree they were pretty metal as well.