I'd like to preface this by saying I am not religious. I don't actually believe in God, Satan, Heaven or Hell.
But if I did, I would side with Satan. He stands for everything I love.
1. Science
Satan gave us knowledge in the garden when he convinced Eve to eat the fruit. This is also a shout out to women, which I also like. Adam was happy to be ignorant, but she wanted more. If it weren't for the Devil, we would all be stupid monkeys still and would have never tried to understand the physical nature of this world. Think about all the lives Satan has saved and all the pain he has helped to alleviate by making us capable of acquiring knowledge.
2. Premarital Sex
Use protection. God calls it a sin, but the Devil knows the truth. Sex is natural and we are meant to do it. Marriage on the other hand is not. Sure, monogamous relationships are beneficial for the survival of a species. We have the power to stop STDs from spreading by using condoms and we can prevent unwanted pregnancies by using them as well as other forms of birth control. We have all the tools to mitigate the dangers of having frequent premarital sex, so we should take full advantage of them!
3. Nature
I'm all about nature and so is the Devil. Think about magic mushrooms and cannabis. These are parts of nature that we can use to expand our understanding of the universe. God might want to limit us in our understanding, but the Devil wants us to experience the universe in its entirety.
If I did have a religion, it would have to be that of randomness and chaos. I believe that life is the universe's way of experiencing itself and that chaos is the mechanism by which it does so.
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I don't prefer Satan that much [spoiler][i]HAIL SITHIS!!![/i][/spoiler]