Satan is a made up entity used to marginalize, brutalize, and scare people.
Throughout the ages anyone different was associated with Satan. Women who served no purpose to men were labeled as witches because they associated with Satan. If you were a woman and smart, old, unattractive to the patriarchy you could be cast out and labeled a witch. If you were Jewish, Gypsy, Native you were ungodly and subject to the whims of church people as to whether you would live or die. The Doctrine of Discovery written by the Holy Church made it allowable to kill anything not perceived as Godlly in the name of greed.
To be a Satanist is to rebel against the Puritanical norms created by those that came and "escaped" religious persecution only to persecute anyone not agreeing with them. To shun patriarchy and white supremacy.
To be a Satanist is to go against the major religions that are grounded in being a faithful servant to a fictional character.
To be a Satanist is to go back to the old religions that worshipped the Earth and water and the things that are beautiful on this Earth and not live for the secular.