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.