I ask this question because it came to mind after some Atheists I know started talking about Satanism, LaVey and the Hebrew roots of the word Satan.
I couldn't help thinking of this image, "Get Thee Behind Me Satan" by James Tissot. It illustrates the incident when Jesus called Peter a Satan, that is, an adversary or accuser. The context? Peter had affirmed Jesus as Messiah, and Jesus immediately predicted his death, the conjunction of which Peter reacted against. It seems Peter had messianic expectations that were more traditional, more militant, more self-righteous, than Jesus.
The image that often lurks behind this Satan language is a court room drama, where their is a defendant, an accuser, and a judge. The accuser was not necessarily evil, but he was no friend of the defendant, innocent or otherwise.
Now, few would argue that a lifestyle licence is Satanic (least of all LaVey!), but what about a lifestyle of legalism? The accuser is aiming to bring you down whether you wander to the left or the right of the justice. Jesus recognized this. Peter wasn't tempting Jesus to go soft. No, he was tempting him to attack his enemies in self-righteous fury.
So it makes me wonder. Fundamentalists often accuse Liberals or being satanic, but isn't the converse equally justified? Jesus seemed to think so. If memory serves me right he called the Pharisees satanic more often than Sinners. And you know what, when I present this image of a self-righteous Satan to Atheists, often they find sin and Satan a lot less attractive. Funny that.