This statement is one of the most ridiculous things anyone could say to an atheist and amazingly it is one of the most common statements made to atheists.
The ridiculousness of the statement is easy to identify. Atheists lack belief in gods and supernatural beings. Satan is a supernatural being. Therefore, atheists lack belief in Satan.
In order to be a Satanist one must believe in Satan. Atheists do not believe in Satan or his alter ego. Satanists believe in Satan and his alter ego. Christians believe in Jesus/Yahweh and their alter ego, Satan. Out of Atheists, Christians, and Satanists, only two believe in Satan: Christians and Satanists. If Christians believe in Satan, does that not make them Satanists? NOTE: Satanism, in its true roots is not the worship of Satan, but the worship of “self” or “ego”. Many people when they think of Satanists have images of “Hollywood Satanism” embedded in their minds. I am using the belief in Satan because Christians actually think of him in this manner.
The usual response I get from this comparison is one of disgust when the Christian realizes they are being associated with their interpretation of Satanists (even though it is clearly facetious and sarcastic). This is actually rather humorous considering the Christian was not worried about associating atheist with Satanism. Do not throw insults if you do not want that insult thrown back at you.

It amazes me that people actually think that Atheists worship Satan. We don’t believe in him, either!
Churches have done a wonderful job of informing believers that atheists are in league with Satan. This actually comes from a statement made by Jesus in the Bible to the effect of “if you are not with me then you are against me.”
“Anyone that is not for God is against him” is usually the way it is phrased. I hear that line a lot. As an Atheist, I am neither for nor against God, because he does not exist. While it often becomes necessary to “attack” the god or gods in order to support arguments that does not mean I am against gods. I only use the irrationality, errors, contradictions, and inconsistencies of the gods to help shine light on the bigger picture of irrational belief in the gods themselves.
Another fallacy of the Satanism argument is that Satan was not the alter ego of God until apologetics needed to take the explanation of evil away from God.
Before monotheism, there were many gods and there was usually a god to explain the evil and bad happenings of this world: gods of the underworld, gods of darkness or gods of the demons. When monotheism evolved then all happenings, good and bad, fell upon the single god. The single god was responsible for good and evil, birth and death, hate and love, and every other pro and con you can think of.
Where does the Old Testament mention Satan? In addition, what is his role when mentioned?
The first mention of Satan in the Bible is in I Chronicles 21:1, which says, “And Satan stood up against Israel, and provoked David to number Israel.”
Satan convinces David to conduct a census of those “who drew the sword.” Joab, the one assigned by David to get the numbers, miscounted by two people (he purposely left out Levi and Benjamin). Because of this and the act of conducting the census, God gave David the choice of three punishments; three years of famine, three months of being defeated by his enemies or three days of “the sword of the Lord”, which was “the plague of the land, with the angel of the Lord destroying throughout all the territory of Israel.”
David chose the punishment of three days and God killed 70,000 Israelites through plague and destroyed Jerusalem.
Maybe it is just me, but who did the most evil and immoral thing in this story? Satan is guilty of convincing David that he needed to know how strong his army was. God killed 70,000 people and destroyed a major city.
How did God make David personally pay for the heinous sin of counting his armed forces? God made David build an alter in a building owned by a man named Ornan, who was a Jebusite. Luckily for David, Ornan the Jebusite let David have the building at no cost and he even gave David the oxen and other stuff for the sacrifice upon the alter.
How is Satan the bad person in this story? I do not see it. The supposedly good God that Christians and Jews believe in performs the only evil deeds performed in this story.

The suffering inflicted upon Job by Bible-Satan at the Bible-God’s behest is a prime example of biblical immorality and the cruel nature of religion and its gods.
The next mention of Satan is in the book of Job. Satan arrives at a gathering of “the sons of the Lord” and God asks him if he has considered Job, who God seems to think is the cream of the crop of believers and those that conduct the required sacrifices at the right time and place. Satan says that if God punishes Job that Job will bad-mouth God. Therefore, God gives Satan permission to mess with Job.
The first thing Satan does is have raiders steal his five hundred oxen and five hundred donkeys and slay the servants tending over them – leaving only one servant alive that could tell Job what happened.
Then Satan burned Job’s seven thousand sheep (the messenger said it was the “fire of God from Heaven”) and killed all the servants except the one that could tell Job what happened. Then Satan sent more raiders to kill Job’s three thousand camels and all the servants tending them except one allowed to tell Job what happened. Then Satan sends a great wind to destroy the house of Job’s children and the house killed them as it collapsed.
Job stood his godly ground and said a prayer to God at hearing this news – he wept none or was angry none – the only thing he did was shave his head and rip off his robe and prayed naked.
However, God was not satisfied. The next time the “sons of the Lord” convene God gives Satan permission to mess with Job directly – to harm his physical body but not kill him. Therefore, Satan gives Job boils over his entire body.
Okay, so again, where is the evil coming from in this story? Satan is doing the dirty work, but he is doing it at the behest of God and with his full permission. Satan is not God’s arch-rival in Job – Satan is God’s helper; the Godfather’s hit man out on a contractual hit.
Another mention of Satan comes in Psalm 109:6, but in many translations the word is “an accuser” and not Satan. The majority of the Bible dictionaries and scholar notes list this as “an adversary” – not as Satan.
The next mention of Satan is in Zechariah 3:1-2, which is where the Lord actually rebukes Satan and says that Jerusalem rebukes Satan.
There is no mention of “Devil” in the Old Testament (KJV). The only mention of “Lucifer” is in Isaiah 14:13 (KJV), which is where Lucifer is the name of the Day Star – not the name of Satan or the Devil.
Christians attribute Satan with the Original Sin and the downfall of humans from the Garden of Eden and the Tree of Knowledge. Yet nowhere in Genesis does it say that Satan was the serpent. The Garden of Eden story, specifically where the doctrine of Original Sin comes from, never mentions Satan.
The bottom line is that the church could not blame their “loving” God for acts of terrorism (both natural and fabricated). They had to have a scapegoat to blame all the evil. Satan was transformed by the early Christian church from God’s right-hand-man into the alter ego of God with the same power and abilities. Satan became a god and Christianity became a polytheistic religion. Of course, you will never get a Christian to admit that Satan is a deity.
Where were we? Oh yeah, I am not a Satanist.