The only solution, if any, is democratic: containing the damage and reducing the numbers. They cannot be persuaded, but other people can. And unfortunately, I don't think that's all that effective, either -- in part because they ally themselves with other conspiracy theorists who insulate them from some of the consequences of their actions. They may not agree, but don't attack each other, and bolster common causes. Enough to win elections, especially when geographic, demographic, and historic quirks assign more political power to some regions than others.

If it were just creationists, they'd be (relatively) harmless kooks. As it is, they're always a step away from theocracy.