The satanic church was started in the 60's by Anton LaVey, so logic would follow that he would be able to define a satanist better than
Oprah or whoever hosts Dateline or 20/20. A satanist doesn't believe in god or satan. A satanist is an atheist that believes people should be
responsible for their actions.
Satanism itself addresses problems it finds with Judeo-Christian beliefs. They find that telling one's children that they should behave correctly not because its the decent thing to do but because some
ridiculous land of fire will make their 'afterlife' really shitty is poor parenting.
The reason why satanists are thought of as scary people in black coats that sacrifice goats and abduct children springs from 2 sources. The first is sensationalist media outlets like Oprah and Dateline and 20/20 and all the daytime talk shows.
The second is
the real reason why people believe these shows and thats the tendency of
Christians to need to find evil where it doesn't exist. Christians themselves tend to be egotistical (because they only follow their faith when convenient) and like to feel more pious and self-righteous by creating an evil boogeyman that doesn't exist so they can blame society's decay on them.
Christian douchebag: Yeah so this
little kid has gone missing, its gotta be the Satanists.
Non-idiot: Hmm, or it could be just a regular criminal.
Christian douchebag: No! Satanists ruin
everything. Satanists make me ignore my faith by beating the hell out of my wife and
sleeping with my secretary! Its okay though, as long as I go to church a lot and tell god I'm sorry for beating up my wife I'm good. Loopholes are great.