I find Satanist's fascinating. When you listen to his prayer it's pretty hard to imagine that they are anything else than atheists trolling Christians. Unless you take the view that they are using religion as a form of ancient psychotherapy.
Almost all Satanists are atheists. The lefty ones, the libertarian ones and the frothing at the mouth Nazi ones. If you did a cross section of YouTube athiests you'd be able to apply pretty much the same labels.
The only exceptions are Theistic Satanists who have a weird hodge-podge of beliefs with Abrahamic and neopagan elements-maybe toss in Lovecraft as well if they're really confused.
I read that there was an actual case of historical Satanism but no sacrifices or whatnot. In Medieval Sweden Satan was a kind of folk saint amongst some of the lower classes who were otherwise tradotionally Christian.
So more your Catholic grandmother who stuffs little portraits of St Peter with dried palm leaves and bottles of holy water into your cars glovebox when you aren't looking than Rosemary's Baby
. Sorry about that.