UFOs are real; that is, there are sightings of things that have not been identified. The whole thing is  based on a sighting by Kenneth Arnold in 1947 that was probably a flight of pelicans and 50s science fiction movies. Arnold described a flight of wedge-shaped objects that flew like saucers skimmed over water. The newspapers got it wrong and called them “flying saucers”, and everyone started seeing saucers and discs. Tropes like missing time, buried memories and alien implants all appeared in 50s films like INVADERS FROM MARS and KILLERS FROM SPACE before anybody reported them in real life; and abductees reported boarding the ship by a ramp, like in the movies, but once STAR TREK came on, they reported being beamed aboard. The people who made the first crop circles admitted it was a hoax. Dr Simon, who brought out abductees Betty and Barney Hills’ abduction story under hypnosis, diagnosed that those were not real memories but a delusion brought on by Betty’s lifelong obsession with UFOs and Barney’s submissiveness to her will. UFOlogists who have brought out other abduction memories don’t tell us that hypnosis does not bring out truth, but only what the hypnotized person thinks the hypnotist wants to hear.  

UFO doesn’t mean alien spaceship; it only means unidentified. Every UFO sighting that has been properly investigated has proved to atmospheric phenomena like lenticular clouds (below), misidentified aircraft, drones, birds, stars, planets, reflections of ground lights, mirages or outright hoaxes. In several cases where clear photos of flying saucers were produced, the miniature models the photographer used were found. There is a known condition called sleep paralysis that causes people to wake unable to move with a strong feeling of being watched; in the middle ages this was blamed on witches - now it’s aliens.

UFOlogists - who have never studied a UFO, only witnesses' stories - have come up with a clever excuse for not having any proof (NOTE: stories, reports, anecdotes, testimony and hearsay are not proof): the government is hiding the truth. Of course they have no proof that the government is hiding anything either.

Think about it. If UFOlogists actually believe in aliens, why haven’t they ever tried to prove it? Have repeat abductees wear a wire. Set up a broadcast signal in their homes such that if the alarm stops, they’d know that aliens were interfering with electronics. Have response teams ready to catch the aliens in the act. They don’t, because they know nothing would happen and they’d be proven wrong.

There is no reason to fear aliens once you understand that they are not real.

13 Reasons To Doubt Aliens

I answered a comment on Quora with a 13 point response to "13 Reasons To Belive in Aliens" at http://nymag.com/intelligencer/2018/03/13-reasons-to-believe-aliens-are-real.html I worked for several hours and then somebody reported it and without contacting me Quora deleted it. I canceled my Quora account but since I didn't want that work to be wasted I'm posting it here.

I was disappointed in “13 Reasons To believe in Aliens”. Was hoping to find some really challenging material to delve into. None of these reasons hold water – except to believe in life somewhere in the millions of galaxies and billions of stars that we know about. Nothing to make anyone think “they” are or ever have been here, and nothing resembling proof.

1 The Government Literally Just Admitted It’s Taking UFOs Seriously

~ Not aliens but UFOs: UNIDENTIFIED Flying Objects. In fact they changed the designation to Unidentified Aerial Phenomena to indicate that they may not be “objects” at all. That allows for atmospheric phenomena like temperature inversions and noctiluscent clouds, radar glitches, delusions and more. It also includes objects but a lot of false reports have been attributed to stars, planets, birds and conventional aircraft. The government is taking the sightings seriously – but not aliens.

2. Harry Reid Says We’re Not Taking Them Seriously Enough

~He does, but what does he know? In Logic this is a form of false reasoning called Argument from Authority. He was interested in “science, and in helping the American public understand what the hell is going on”, and from a security viewpoint. I have yet to find an interview where he even mentions the possibility of aliens. In fact he said he didn't want to talk about “little green men”.

3. Scientists Are Suddenly Much More Bullish About the Possibility of Life Out There

~Obviously, as we find more and more Earthlike planets, scientists are more convinced that life exists out there Out there – they said nothing about aliens here, and nothing to do with UFOs.

4. THEY’RE ESPECIALLY BULLISH ABOUT THESE PLANETS

~ See 3 above; this is one “reason” split into two. Again, they're talking life on other planets – possibly microbial life - not aliens visiting here.

5. AND THERE IS “DOCUMENTATION”

~Seriously? Some people drew some pictures??

6. THAT “ASTEROID” LOOKS AN AWFUL LOT LIKE A ROCKET SHIP

~ … but is really just an asteroid. It has shown characteristics we'd expect from a natural comet-like object ejected from a distant solar system. In fact the “looks like a rocket ship” shape argues against it being an alien vessel. Rockets are insufficient for traveling the distances between stars.

7. THESE MASTERS OF THE UNIVERSE ARE OBSESSED (THEY ARE ALSO ALL MEN)

~They are “obsessed” with space travel, searching for primitive life in the Solar system and finding intelligent signals with SETI. Again, this has nothing to do with UFOs or aliens on Earth.

8. AS ARE SOME PROMINENT MILITARY AND GOVERNMENT FOLKS

~Again, Argument from Authority. Prominent people are just as subject to false beliefs as anybody else. Notice that none of them has any solid evidence.

9. (AND THIS GENIUS THINKS HE CAN TALK TO THEM)

~That's totally misleading. Wolfram speculates on how to communicate with hypothetical aliens. He never claimed he talked to them.

10. THERE HAVE BEEN ENOUGH WELL-KNOWN ENCOUNTERS TO FILL ENCYCLOPEDIAS

!Besides the obvious fact that the number of people who claim something does not make it any more true, (Argument from Popularity; thousands of kids who believe in Santa Claus does not make him real), many of these well-known encounters have been investigated and put to rest. Of course the documentaries and UFO books tend to cover up that part.

Barney and Betty Hill for one: Their abduction was recovered by regressive hypnosis, but the doctor who brought it out stated that the memories were not real but a fantasy based on Betty's dreams. Betty was obsessed with UFOs and hoping to see one well before their “encounter”. Even UFOlogist John Oswald stated, "She is not really seeing UFOs, but she is calling them that." On the night they went out together, "Mrs. Hill was unable to distinguish between a landed UFO and a streetlight". Barney drew a picture of an alien from that week's Outer Limits show but changed his description when he overheard Betty's story. Barney saw a row of windows with beings looking out. From the direction he was looking, and the time and date, it now seems clear that he saw the Cannon Mountain Aerial Tramway. Its cars are a pretty close match for what he described and for the picture he also drew.

12. WE EVEN HAVE SOME PRETTY DEVELOPED THEORIES ABOUT WHY WE HAVEN’T HEARD FROM ET YET

~Again, speculation about “out there”. Nothing to do with aliens here.

13. AND IN THE MEANTIME, ALIENS CAN BE WHATEVER WE WANT THEM TO BE

How is that supposed to be a reason to believe? Notice how it states that reports began becoming more coherent and similar in the 40s and 50s? That's when pulp magazines and movies began popularizing aliens. The tall blond men and women were straight out of Amazing Stories, and the 50s movies introduced most of the tropes of UFOlogy – before people began imagining them in real life. Missing time, repressed memories, big eyes, alien implants had appeared in films like It Came From Outer Space, Killers From Space and Invaders From Mars and the urban legend that is UFOs swallowed them up. It is very telling that until Star Trek came on, abductees went aboard UFOs on ramps like in those films, but after Star Trek people reported being “beamed” aboard.