Doesn't Satanism presuppose Christianity?
It is true that Satanism, as a resistance movement against the Christian faith, could not logically precede that which it resists; but it must be understood that the term 'Satanism' is itself a pejorative label that Christians have historically applied to all non-Christian religions going all the way back to St. Paul who, in his epistle to Corinthians, accuses the 'gentiles' -- that is, all those who do not worship his Jewish god -- of sacrificing to demons ( 1 Corinthians 10.20 ). So, as far as Christians are concerned, EVERYONE who doesn't worship their god is a de facto Satanist. Modern self-styled Satanists are only taking the Christians at their word rather than engaging them in fruitless semantic or theological debates over the definition of 'Satanism'.
Satanic values are indeed broadly identical to those of atheists and religious moderates inasmuch as those types of people tend to embrace some form of Humanism. But it must be kept in mind that, from a Christian perspective, Humanism is a thoroughly satanic philosophy that, as implied in its very name, posits human beings as objects of ultimate concern, rather than God who created humans to begin with.
Humanism is founded upon the primacy of man, not God. Humanism recognizes the inherent value of human life wheres the Bible says that humans are rebellious sinners who all deserve to die (Romans 6.23).
Humanism teaches that men and women are equals, but the Bible says that women are not equal to men; that women are to men as men are to God (1 Corinthians 11.3).
Humanism says that children are to be treated with the same respect as adults; that they are to be guided and nurtured, not dictated to and exploited -- but the Bible says that children who do not obey their parents are to be executed (Deuteronomy 21.18-21), that little girls should be raped (Numbers 31.17-18), and that the infants of the enemy should have their heads caved in (Psalms 137.9).
So you see: you must choose. Will you follow God's word or Satan's secular humanist ethics? I've made my choice. I choose liberty, equality, and brotherhood with all life. I choose Satan!