Finally convinced an acquaintance that chemtrails aren't real. He might not be 100% convinced, but he's definitely giving the whole notion heightened scrutiny. While chatting with believers online, he's brought up various points that I've made to him about contrails/chemtrails ; they responded with anger, suspicion, accusations, and did not really address his questions. Minor victory, but I honestly thought that he'd never change his mind.
Within the past month or two. He was quietly mulling over statements like, "Chemtrails are simply impossible because A and B," and surprised me by asking me to elaborate. He'd obviously spent some time considering it.