I've thought about that and a few days ago too. I was thinking about the behavior of ghosts / demons, non-sinning angels, humans and aliens, and have concluded that aliens do not fit into the category of demons:
1. Demons are interested in causing strife, does flying around in a ufo or appearing as an alien and showing themselves collecting some plants have that effect, even indirectly to any great degree? It's as useful as pretending to be a human with purple skin, walking by someone's house, and hoping an argument will arise over someone seeing a purple guy walking by, which is absurd. Demons may be immoral to the point of occasional stupidity, but in my educated opinion that is too stupid even for a demon to spend their time on. There known behaviors are this:
a) They love appearing in photos as humans, animals or perhaps showing an occasional object related to the history of an area. The obvious idea they are trying to convey is that there is no heaven or hell or that the Bible is a lie because God doesn't really make an unsaved person "sleep" or end up in Hell and they can just wander around or go to a higher plane etc.
b) They love scaring people:
b1) messing with objects, like throwing them around or making them appear in another place. The idea behind that is related to a. and to get people to fear or be in awe of them rather then god.
b2) Demons often physically harm people, either the people they possess or those they rule over, and in many different ways. The worst aliens are known for doing, and it's rare, is helping one army defeat another, a few instances of kidnapping, and maybe two or three of mass kidnappings, destroying jets that were pursuing them, giving people one or few minor scars, temporarily suppressing scary memories (is that what a demon would do?) causing electronic interference, destroying the space shuttle Columbia, destroying the space tether, destroying a Russian probe going near the moon called Phobos, and supposedly giving false gospels or making the false claim that they've been genetically engineering humans in mass. All those acts of violence or defensive behavior are very rare. Over a period of 5000 years that's the worst most people can think of, unless you include the supposed butt probing and alien breeding. Now, compare those incidents with the mass murder of Christians and people of various ethnicities. How does that compare? The two behaviors are very distinct: Demons are frequently violent, and often boastfully so, and aliens are hardly ever around and apparently don't do much but explore and take a break, as if they were tourists.
c) Assuming Satan goes about like a roaring lion and that that means he regularly possesses people and gets them to do evil, such as preaching false gospels and committing major acts of violence, why then do so few aliens behave the same way? Why aren't aliens regularly committing violent acts to the point of ending up committing suicide or accidentally ramming homes and trees just like a human being violent or who is drunk? If aliens are the ones responsible for kidnapping people all the time, why are so few aliens caught doing so? Why do so many show up dazzling, using tractor beams, or having to get people to come out and get you? Why wouldn't God want us to know that Satan is the one making people disappear? Furthermore, since when to people simply vanish? What's Satan doing, burying them 400 feet underground? Making them reappear in space? What kind of violent act is that? If he's that powerful why not make them reappear in a jail cell of a violent person to be raped and have their body scattered all over the ground? That way stories would spread about loved ones being raped or their bodies being found scattered all over. An example of Satan's known style is to get a person kidnapped, tortured maybe, then they get buried in place that is sometimes found. Then the parents or friends sometimes find out and turn against God usually more so then before. But making a person disappear, and not even hinting to anyone that it was caused by a UFO or hardly ever doing so, is that his style? And how tormented would a foolish person who thinks aliens are friendly? Surely Satan knows that there a great many people who think all aliens are friendly, so then why would he choose such a poor means of tormenting anyone? And sure he knows that God would not let him simply vanish the human race by making them disappear to who knows where if that is his true intent as some might argue.
Now contrast the frequency of human and animal violence to that of aliens. If aliens are demons because aliens sometimes scar people that would make all humans demons as well, and animals. You could even argue trees were demons then because trees sometimes scratch and kill people.
d) They attempt to tempt people to commit sins in general, such as how Satan "rose up against" David, which I think was done by possessing someone who was not saved and having that person get David to count his army. I used to think Satan maybe influenced David's thoughts, but I realized the Spirit is in control of the mind of those who are saved, not Satan, and I seriously doubt the Spirit opens a person up for an occasional attack. Assuming Saul was saved the spirit that tormented can be explained as it either whispering hellish things in his ear and or causing him some sort of physical pain. Do aliens do that? Has anyone ever reported the appearance of a UFO coinciding with someone being tormented with a demon? I've never heard of such a thing in my many years worth of studying UFO's and ghosts / demons. How is an alien floating in the air often from very far away and then zipping away or slowly floating away, or crashing into the ground, an attempt at getting you to sin? You might as well say the moon is a demon, that birds are demons, and that anything unclear you can't make out or that is very strange to you is a demon or Satanic. Remember what the Catholics did to Galileo? That's where that kind of flawed logic leads.
e) Some demons love to frequent or stay at a certain spot, a very limited area usually. There are only a very few stories of false humans (demons pretending to be humans). These stories are about a few ghost hitchhikers who were in the image of formerly living persons. UFO's on the other hand are almost always seen traveling great distances or only showing up a few times in the space of a week. As for UFO's caught by infrared cameras, there are no reports of these UFO's coming back to the same spot and interestingly, no ghosts have been caught floating around in the air or sky using infrared cameras. As for ghosts caught on infrared cameras in homes, why are they always in the shape of blobs or something living like an animal or human rather than a disc, cigar or saucer shape if it's really demons who are making such things? Are demons not clever enough to try and trick people into thinking UFO's also explore the interior of homes? What would make more sense is that UFO's do not enter into homes is because the aliens in them can easily observe humans from outside or remove them or do not want to accidentally damage a person's home or their ship (which could happen if the ship were to revert to being solid). The risk of aliens or ships being destroyed by merging with solid objects explains why they becoming solid again before entering oceans or lakes and are never seen passing straight through mountains or the ground or even going into them a little whether in solid or in a "higher vibratory" form.
f) If demons can frequently appear as aliens and UFO's, why not anything else? Why not appear as planets, asteroids, animals, plants, humans, cars, needles, x-ray machines, computers, and on and on. Is there some demon with a "let's look like weird people and boringly shaped ships that sometimes shut off electrical things and kidnap you, get you pregnant and then take the baby off your hands, crash, and mess with wheat fields making pretty designs and not even destroying the wheat, and occasionally go under and out of the lakes and oceans" fetish? That's too bizarre to believe. Even if there was a demon with such a fetish, why is it so narrow as not to include UFO's traveling in and out of the ground, straight through mountains, floating through trees and buildings? Instead they avoid touching anything but the top of the ground, and that's only to land. Ghosts / demons pretending to be human spirits or just being themselves do not give a consistent display of carrying about not doing things that would give the appearance that they were not solid.
g) Demons possess people. Do aliens possess people? Supposedly some claim they do, but there is no evidence for their claims. They haven't gone off and built alien technology or anything that can be verified as being so strange that it surely must have been something from an alien civilization.
h) Demons communicate with a person either verbally or possess them and talk into their mind for lack of a better explanation. Aliens either use verbal, sign language, or telepathy.
Conclusion:
The behavior of aliens does not match demons, only occasionally. and there is no evidence I know of to say, "An alien broke this law of God". There is no evidence that aliens are bound by human laws any more than animals. Their behavior matches more that of angels. In order for them to have developed extremely advanced technology they would have to have a very high desire to learn how better to survive and explore and to avoid strife which would hinder survival and exploration. We know that strife-lovers horde wealth and centralize power to the point where only other strife-lovers have it. They cause the majority of people to be stuck in a limited area, Earth. We know that strife-lovers are materialistic and love causing even strife among themselves. This does not seem to lead to interplanetary exploration on a weekly basis let alone intergalactic. If there is such going on, it's obviously on a very small scale from what was learned about the activities at Area 51, which wasn't that big a deal. The behavior of aliens matches that of beings who God has either restrained to be very peaceful with very little evil behavior, or who he has kept entirely sinless like certain angels and animals who don't harm any humans.
There is the sea, vast and spacious,
teeming with creatures beyond number—
living things both large and small.
There the ships go to and fro,
and the leviathan,
which you formed to frolic there.
These all look to you
to give them their food
at the proper time.
Psalm 104:25-27
