It depends on how you define 'Satan'. The followers of Anton LaVey, for example, do not worship a red, horned demonic-style being from the Bible, but are essentially hedonists, yet describe themselves as being Satanists. Satan is used in a symbolic sense as representing human desire. They're quite silly, but essentially harmless and are quite big on whatever you do not hurting anyone else and being consensual.
Then there's the sort of Satanists who basically worship the Satan of the Bible, though they claim he's misrepresented by it. They're even sillier, but potentially the sort of nutter who might do something morally dubious in the pursuit of their religion.