In college, one of my roommates was preparing for seminary school. He had a book on cults. There was a chapter on aliens and this is about what it said.
The aliens were really the fallen angels...demons if you will.
It was all Satanic.
Truthfully, there are lots of problems with the time and distance required for a carbon- or silicone-based life form to travel to Earth. And yet, we discuss and debate the topic and usually fly off into fantasyland.
If you are a Believer, the demonic theory is very compelling. Indeed, just like how people often say prayers in the midst of difficulty and obtain relief, I wonder how "alien abductees" would fare if they recite the Lord's Prayer.