Believing in Satanism, does not mean being antichrist but the fact that there is always two sides to a coin.
Some structures, and issues, are polyhedral, with more than two sides.
Day and night always goes hand in hand.
They grade into each other. Hence, 'dawn' and 'dusk.'
I'd shirk from using binary logic to delineate all facets of the philosophy of Satanism. Not every issue is presentable via two sides, and even if an issue only has two sides doesn't mean that they are weighted in equal proportions of merit.
"What a book a Devil's Chaplain might write on the clumsy, wasteful, blundering low and horridly cruel works of nature."-Charles Darwin, letter to Joseph Hooker
"The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, and no good, nothing but blind, pitiless indifference."-Richard Dawkins, River Out of Eden: A Darwinian View of Life