Unfortunately, there's just enough "proof" behind Chemtrails (Agent Orange, Cloud seeding) for them to cling onto. Somewhere along the way they added 2 and 2 to get purple. In their minds, Contrails are now the conspiracy
Thanks to apps and websites like flight radar, every chemtard is able to run outside with a cellphone and take "undeniable proof" of Chemtrails while then linking it back to X Airline innocently flying overhead.
Plenty of websites and facebook pages devoted "exposing the truth".