You can't be both an atheist (someone who doesn't believe in the existence of any supernatural beings) and a Satanist (someone who believes in the existence of at least one supernatural being). If you read the actual article you learn that Steve Hill is just an atheist but he calls himself a "Satanist" because he agrees with the modern Satanist church's strict belief in the separation of church and state. But that doesn't make him an actual Satanist, any more than an atheists who expresses admiration of Christian organization's dedication to the poor is a "Christian."
This is really just a hook to get attention. (As Hill himself admits: "I’m a Satanist as far as trying to get people to understand that I don’t believe in the devil any more than I believe in God... All of it is stupid. But if I have to tell people I’m the devil to get them to listen, then, OK, I’m the devil.”) But as an atheist myself, I would prefer that Hill drop the Satanism shtick and defend atheism on its own terms, without perpetuating the myth that atheists are like devil-worshippers.
This is really just a hook to get attention. (As Hill himself admits: "I’m a Satanist as far as trying to get people to understand that I don’t believe in the devil any more than I believe in God... All of it is stupid. But if I have to tell people I’m the devil to get them to listen, then, OK, I’m the devil.”) But as an atheist myself, I would prefer that Hill drop the Satanism shtick and defend atheism on its own terms, without perpetuating the myth that atheists are like devil-worshippers.