Credit where credit is due
I'm not "sold" on their existence, either. As a matter of fact, I made a statement where I mused perhaps it was a government or military experiment. However they've been around a lot longer than that. We just don't know what they are yet, or we haven't invented a device that can capture and monitor them.
This is a much more reasonable viewpoint than Friedman's.
I know there's some psychological aspect to it (by which I don't mean anything like "nuts"). I did a lot of looking at this stuff in my younger days, and one thing I noticed in sightings back a hundred years or so is that the vehicles always seemed to be just beyond whatever the current technology was. In the 1800s, people saw mysterious airships.