When I was a teenager, I went to church, and almost every ‘Christian’ there was a complete asshole. What makes it worse is that they try to justify it. This honestly made me think that if God and Satan were real, I’d want to know Lucifer’s story. Maybe he’s not actually ‘evil.’
Have you read the Bible? The only evil shit that Satan does is when he fucks up Job's life, and that's in collusion with God. Meanwhile, God is doing evil on almost every page of the Old Testament.
The reason we're supposed to hate Satan is because he rebelled against God. Again, if you've read the Old Testament, you have dozens of good reasons to rebel against God.
This train of thought is what lead to the creation of Satanism as a literary movement in the 19th century and then as a religion in the late 20th century.