The information is next to the flat earth section at the library. You won't get reasonable or logical arguments out of anyone who believes all planes are dumping chemicals into the sky.
Discussion
The "all planes" thing used to be the thing, I don't know if that's the claim they're making now. Changing claims with time is a red flag, but I'm still willing to consider it if I see something compelling. Right now I'm in your camp on this one, but I'm always willing to be shown my own ignorance.