Metal ALWAYS carried some questionable imagery, even in the days of Hair Metal and stage theatrics. It was either intended to be offensive, bleak, or just too loud for the squares to handle
Despite being the logical next step in the taboo, Satanic imagery isn't that rampant in metal... I could even go as far as to say it's confined to Black Metal nowadays. With the exception of say, Immolation or Incantation, Death Metal has always been rooted lyrically in the field of violence or horror, with little to no impact on their image or live shows. Grind is generally socio-politico or absurdly gorey/campy, and Thrash has it's left-handed moments, but they're not all Slayer or Dark Angel descendents.
It's always been stupid, but the counter bands are even worse.