As used here "UFO-crazy" wasn't a supposition, it was a constraint.
"UFO-crazy uncles" are known to exist. This is not an extraordinary claim. The existence of such uncles provides no evidence for or against extraterrestrial visitors or other aerial phenomena.
In context seemed more like a smear for any who don't dismiss as unremarkable. But I'm glad you took it as the narrow case, tho - do they really "exist", or might they have just been right all along? Lol
People who believe in "chemtrails" are (in my un-scientific survey) pretty likely to be conspiracy enthusiasts ("cranks", "crazy", etc.).
But they're not wrong that the stuff coming out of the back of jet aircraft is changing the climate.
Small, localized weather engineering programs have long been real (cloud seeding), and planetary-scale climate engineering projects are now openly discussed by governments. E.g. https://www.epa.gov/geoengineering/about-geoengineering "Types of solar geoengineering techniques include: Stratospheric Aerosol Injection (SAI) – adding small reflective particles to the upper atmosphere (stratosphere) to reflect incoming sunlight. Sulfur dioxide (SO2), one of the types of chemicals considered for SAI, can chemically react in the stratosphere to form reflective sulfate aerosols."
And then a counter example of something broadly accepted but untrue. The humoral theory and blood letting, practiced for thousands of years. This is what killed George Washington.
