“To argue with a person who has renounced the use of reason is like administering medicine to the dead.”

Thomas Paine
American Founding Father and author of the Revolutionary-era pamphlet Common Sense.

Common sense tells us to pick our battles. There is little point in arguing with zealots because they are unfazed by the use of logical arguments. It is highly unlikely that anything said will make them stop and re-evaluate their beliefs. FSM knows I used to be like that when I was gripped in the throes of the conservative political dogma.

The only time I know to engage the zealot is when there is a third-party that can be swayed. In one of the great scenes from the movie Thank You For Smoking, the protagonist, Nick is explaining his job as a lobbyist to his son, Joey.

Nick: Okay, let's say that you're defending chocolate and I'm defending vanilla. Now, if I were to say to you, "Vanilla's the best flavor ice cream", you'd say …?
Joey: "No, chocolate is."
Nick: Exactly. But you can't win that argument. So, I'll ask you: So you think chocolate is the end-all and be-all of ice cream, do you?
Joey: It's the best ice cream; I wouldn't order any other.
Nick: Oh. So it's all chocolate for you, is it?
Joey: Yes, chocolate is all I need.
Nick: Well, I need more than chocolate. And for that matter, I need more than vanilla. I believe that we need freedom and choice when it comes to our ice cream, and that, Joey Naylor, that is the definition of liberty.
Joey: But that's not what we're talking about.
Nick: Ah, but that's what I'm talking about.
Joey: But … you didn't prove that vanilla's the best.
Nick: I didn't have to. I proved that you're wrong, and if you're wrong, I'm right.
Joey: But you still didn't convince me.
Nick: Because I'm not after you. I'm after them. (Pointing to by-standers)

We’re not trying to convince the zealots, we’re trying to convince them. The by-standers that will listen to reasoned arguments against the rhetoric. Those who can be swayed.