From the Outsider Satanism website:
Outsider Satanism is a sect of modern Satanism. We are working to articulate a philosophy that refines what’s been laid before us by Anton LaVey’s Satanic Bible, The Satanic Temple, and other satanic works.
Outsider Satanism is a natural evolution of those earlier concepts. With the advantage of hindsight and experience, we can look back at pre-existing satanic philosophies and build upon them in a way that creates a more rational, natural fit for the modern satanist. Gone are the days when one would be forced to choose between two opposing extremes who mirror the behavior of modern American political parties, whose goal is to be as contrary to one another as possible, while dumbing down the message in order to capture a larger audience. This dichotomy simply doesn’t work for the critical thinker.
Citing the Church of Satan and The Satanic Temple as primary sources of modern Satanic ideologies, we compare and contrast them, adding to and subtracting from them as needed. The end result is a Satanic philosophy that crosses boundaries of cultural identity, political party affiliation, and social stratum, leaving us with a well defined sect of modern Satanism for the mature, open-minded nonconformist.