Most people are just ignorant... other people, like the guy you just mentioned, are probably just horribly stupid on many levels and there's no way to talk to them about these kinds of things.
I would probably just try to avoid him and others like him (like I do with most people). But you could aslo find out what kind of things he likes and find a way to irritate him. Maybe if he is a god-fearing Christian, you could talk about your website. Or, like I have suggested in the past, light something (the Bible, religious literature, etc.) on fire and pee on it...