People say Christianity is ridiculous, and now you throw in flying demons from outer space 
To be serious, though, I think you might be reading this backwards. Remember the attitude of ancient humans towards anything foreign. Anything which looked or behaved different to them was evil and inhuman (not literally...or is it?). This has repeated itself throughout history. Now, if slightly different skin tone and facial features made them think this, then imagine their reaction when (if) they saw a being more intelligent than us, but adapted to life on a completely different planet. Imagine then how they felt when they realised just how powerful these strange monsters turned out to be.
Wouldn't they be angry? Afraid? Wouldn't they embed these things in their culture, and write about them when they gained the technology to do so? Wouldn't they tell this to their children and their grandchildren so it was passed down the generations?
You speak as though religious texts are absolute truth. Even if you do believe in Christianity, you have to admit that no human can possibly hear and express the exact word of God, right? I believe that is part of Islam - Sharia law can never be perfectly expressed, because it is divine. Some subjectivity from the author has to come into it. Their fears and superstitions. The fears and superstitions of ancient people.
Just because the alien are different, doesn't mean that they are evil. We know that now. If they wanted to destroy the lot of us, they could have done so. If, for some bizarre reason, they wanted to make us all burn copies of the Bible and dance around a fire worshipping an evil red person with large horns, they could have done that too.
Now, 99.999999999999999999999999999% of alien sightings are most probably either the creations of deluded/exhausted minds or people who are desperate to be famous. The following applies for these as well as any people who may have actually experienced evil alien "satanic actions": You find refuge and comfort in what you know. If all of your life you have been a devout Christian and have believed in your heart that Christ was the saviour of all humanity, what is going to happen when you imagine the personification of salvation and security? Of course you'll feel better!
None of this proves the truth of Christianity or the nature of UFOs.
(Former) Lead Moderator and (Eternal) VGC Detective 
