Well, since most of human nature tends to side with the forces of good over evil, Satanism is probably very much a fringe religion with very few actual participants.... so no, they don't have the numbers or the power to do much of anything as dramatic as genocide.
Truthfully... All genocides are not of God, they are of man. Even the ones done in God's name. Man is his own worst enemy.
As I don't believe in god or satan..then genocides get attributed to causes, factions, political beliefs, ethnicities, religions or nations in my world.
Christianity, thus far, holds the record for genocides in this regard. The other big two are distantly behind that religion.
But it's interesting that "Satanic" worship gets the blame for the world's "evils".
Especially given the propensity to "purify" souls via "releasing" them. No?