"Funny, I don't think I've ever had a conversation about gun control with my friends; but I've had several about theocracy."
Just ask them if they think America was a theocracy when John F Kennedy, Harry Truman and FDR were President.
Whether they say "yes" or "no", it will prove the point that their fears of theocracy coming from the modern-day GOP are groundless.
Ask them what today's Christian Right would do that would make America any more 'theocratic' that it was under JFK?
Answer: Nothing.
If they have issues, it is not about 'theocracy' but about cultural assumption and parochial views of other groups in America.
That wopuldn't be my answer. Christian Reconstructionists, for example, would replace our law with Biblical Law. That's, for sure, far more theocratic than the US under JFK.