The common sentiment that shows up when talking about people who believe in these outlandish conspiracies is that "you can't reason someone out of a belief that they didn't reason themselves into", or some variant of that. While I think a lot of people may read that and think that it means these people can't be helped, I think it's more that the method you described, a method based in science and reason, will not resonate with them. While I unfortunately don't have any concrete advice about how to help these people, I can say that a more humanistic approach is probably a better bet.