As I've stated before, I would be extremely polite, thank them for their visit and tell them I wasn't interested. Not in a million years would I attempt to start a biblical discussion with a dub or to think that I could (or even wanted to) get them 'thinking'. This is what I have done the handful of times they have come to my house in FS.
Once I was in my garage waxing my car and two dubs approached me. They were pleasant as was I. They pursued a bit when I kindly told them I wasn't interested. I briefly mentioned that I had been a dub, appreciated and understood what they were doing but I had moved on beyond that. They thanked me and left; a good time was had by all.
Different strokes, but I can't imagine any universe where I would attempt to have a religious discussion with anyone, especially dubs. And I don't give a flying eft what they believe any longer. It is almost impossible to get ex-dubs on this site to truly open their minds; thinking that I could get a current dub to do so approaches the impossible.
And I would rather wax my car.