Here at Rocko's Perspective, we keep finding solutions to everyone's problem. But 25.0765% of the letters I receive have a common problem -- they knock on your door and scare you with fire and brimstone. Yes, you know where I'm heading.
They might be annoying at times, to the point of throwing the Panzer Kitchenware Anti-Gravity Pots and Pans at them. Well, that might shoo them away, but they'll come back for more.
A polite conversation will help them leave you alone, but if some of them insist on converting to their ideals called "Fundamentalism," either you let the dogs out or you call the cops.
I myself have some experiences with these kinds of guys, but what I end up doing is hiding their posts/tweets on my Facebook/twitter page. And block them.
So, if they knock on the door, you know what to do. Also, tell them that everyone has their right to choose what is theirs. Or, take the matter into court.