It would be fairly easy to prove the existence of nefarious chemtrails...a fleet of air worthy drones ready for immediate takeoff which can collect the air around, in, and below the chemtrails. Analyze the air samples on the ground using routine chemical analysis, such as glc, mass spec. hplc, nmr,etc.
With today’s high tech, chemicals, weapons, tools, just postulating toxic chemtrails or denying their existence is not enough to convince anyone. For sure, there is enough bad stuff (some natural) in our air and water and soil already.
On what planet is that "fairly easy"? And who, other than the very government in question, would own such a fleet of high-altitude drones?