Aliens = demons = people
Demons are figurative humans who have decided to pursue a life of malevolance. They've carried out so much horror that they've become a shell of a human. I'm not ready to submit to extraterrestrial aliens until things get further along the proof spectrum.
I am, however, perfectly willing to accept that there are horrible deeds done in the name of the evil that strikes man's heart. The bible is meant to be taken and analyized at a metaphoric level. Demons in the figurative sense would be evil humans who abduct, torture, consume, and pursue lives enveloped in malevolance. Angels would be the agents of good that carry forward the ideal cultural Norms.
Is Satan real?
>No
Is the idea of Satan real?
>Yes. Absolutely.
The same is true for God. God is the result of millenia of exemplary drama told to each generation. God is the guideline for how to live within Western culture so that the culture will succeed. Satan is the mirror of that. The "exemplary" drama created by those who pursue that life.