You’re only commenting on abductions, not UFO sightings. The violent nature of abductions by unusual creatures would produced those feelings. I can only imagine how and alien would view it, if nazis had gone to another world. But that wouldn’t make the nazis demons, only evil.
As for demonic actions, like the sexual reports. Many believers view other religions as demonically influenced, which would include evil behavior such as sexual abductions. Alien religions, if any, would not likely be based on Christ, and therefore likely a form of devil worship. What’s kind of behavior do you expect from alien sinners?
And there are reports in sightings of more than one race. Some have been seen as fairly benign, and only the more aggressive and curious would risk and physical encounter. Whatever they are, judging the actions of one group to represent them all is risky.
Most sightings are mistaken events, easily explained away. Some are hoaxes. But many are buy reputable people. I’m certain and air force or airline pilot can recognize a ship. And most of what is going on doesn’t resemble biblical demonic activity. That usually involved posession, not abduction.
I would suggested looking at Medieval accounts be done with a grain of salt. Everything they didn’t understand was deamed demonic and embellished in stories.
I am only commenting on abductions (though abductions usually involve a craft or what would be described as a UFO).
And you are again correct in that some "aliens" are described as benign (and they might indeed be benign...or those describing them might have developed Stockholm syndrome).