According to the Monasterians, UFO is a demonic phenomenon. I've seen images of children having deformities that made them to look like aliens. Could it be an explanation for the UFO phenomeon? And did the demons model the UFOs after children with such deformities?

Most Holy Family Monastery. That's it.
There are museums with weird birth defects exhibited, like The Chicken Baby of Leipzig or a skeleton of a four months old infant which resembles aliens. I think that demons may source their ideas from these cases to build up aliens.

I never read the Dimond brothers' book on UFOs. I wonder if UFOs really are demons.

If you can get a copy of Jacques Vallee's "Messengers of Deception" you will likely feel it is safe to conclude UFOs are demonic in origin.

UFO's are demonic, just like ghosts and all that other new age BS.    

Not being able to identify a flying object does not make it demonic.

How can one know the nature of something one cannot identify?

New Age BS is...BS. It does not lead people to God, but it is not a demon.

St. Paul in Scripture addresses the nature of idols:

Now concerning those things that are sacrificed to idols, we know that we all have knowledge. Knowledge puffeth up; but charity edifieth. And if any man think that he knoweth any thing, he hath not yet known as he ought to know.  But if any man love God, the same is known by him. But as for the meats that are sacrificed to idols, we know that an idol is nothing in the world, and that there is no God but one. For although there be that are called gods, either in heaven or on earth (for there be gods many, and lords many).

Yet to us there is but one God, the Father, of whom are all things, and we unto him; and one Lord Jesus Christ, by whom are all things, and we by him. But there is not knowledge in every one. For some until this present, with conscience of the idol: eat as a thing sacrificed to an idol, and their conscience, being weak, is defiled.

Treating idols as if they were real beings was a sign of weakness and ignorance. It was to avoid scandalizing people who were so ignorant and weak that he advised not to eat such meat, however, the idols are stated as being "nothing".

Now, if an idol or other false "god" reacts, interacts, or otherwise shows power, it is a demon, but human creations are nothing.

"Aliens" are a popular culture creation, based on TV shows and human desire for entertainment. It appeals to many, and the mentally ill, confused, or otherwise not rational people may make claims about them.

If some being exhibited unnatural abilities, then we could be suspicious of demonic activity, but to treat these things as legitimate phenomena is not proper or rational.

We cannot treat the popular conception of alien activity (inter dimension beings, etc) as reflecting any sort of reality. It is Pokemon essentially. Human imagination and entertainment.

If we had evidence of a fire breathing lizard evolving into a winged dragon-like creature, then we can suspect something, but otherwise, it is a human game, not to be taken seriously in itself.

I wonder if someone will try to submit this post to Matthew as being ban-worthy:

Quoting someone involved in game design:

What is even more interesting is that if you take the average Asian face, then exaggerate the difference from the average by a large factor (there is a function for this called "caricature") you end up with your stereotypical "grey" alien. Therefore I speculate that Greys are just cartoonish exaggerations of Asian features thrown up by the subconscious mind.

A lot of the qualities attributed to Greys seem to correspond to negative stereotypes of Asians too: robotic, souless, devoid of emotion materialistic, prone to conducting bizarre experiments and mutilations on humans and animals, desirous of our DNA to create "hybrids" etc.

I wonder if someone will try to submit this post to Matthew as being ban-worthy:

Quoting someone involved in game design:

What is even more interesting is that if you take the average Asian face, then exaggerate the difference from the average by a large factor (there is a function for this called "caricature") you end up with your stereotypical "grey" alien. Therefore I speculate that Greys are just cartoonish exaggerations of Asian features thrown up by the subconscious mind.

A lot of the qualities attributed to Greys seem to correspond to negative stereotypes of Asians too: robotic, souless, devoid of emotion materialistic, prone to conducting bizarre experiments and mutilations on humans and animals, desirous of our DNA to create "hybrids" etc.

Incidentally, the guy who said this is married to a Korean woman.

What kind of forum substitutes discussion with clicking images?

Most of today's "UFOs" are likely from Area 51.

I would not be surprised if the UFOs are indeed just secret advanced aircraft owned by the military. I think that is more likely than demonic activity, but who knows what powers the devil has.