What is Satan? To me, I would say Satan is what another person doesn't like about me, but is natural to me, and I quite like.
Worship of Satan? Without putting any deep thought into it, I would say just another controlled religion that believes in things that just don't make sense, where any rational mind coud take clues etc and figure out the impossibiity of such a thing.
I think anything that has Satan and worship, is pretty much the same as having God and worship, but just using Satan in place of God.
In that case, I can't comprehend anyone claiming to be free thinking who worships anything fictional, and clearly fictional, unless it is for reasons of fantasy, and that just happens to be that perons release.