I thought satanism is when you don't think there's a god but some evil god person. like satan. but you don't have to worship it. :v
Satanism has basically become so twisted by the media and used by people like a tissue at flu season that it's become so diverse in definition and usage. A bit like every other religion. Just with extra spicy controversy sprinkled on top.
But it is this view of it that people think of it all, which is understandable. The people that use it as a statement are basically overshadowed by that small populace of those who truly believe that there is an evil being, such as Satan, that presides over the Universe and worships him for being as such. But then again, many who take the aggressive Atheist position like the attention that it brings or the controversy it stirs.