I had some similar Bible thumpers/Mormons/Jehovah's Witnesses at my door a great number of years ago trying to convert me.
One of them said "But you must have believed in Jesus at one time?" I replied, "Yes, and I also used to believe in Santa Claus! Goodbye" and went to close the door, but he stuck his foot in the way, saying "But......" and he got no further because I said "Take your foot off my doorstep or I'll break it - now b****r off and don't bother me again." My Scottish wife at the time commented "There was no need for that, you could have just said you were busy, and didn't have time to talk to them". I replied "Yes, and what excuse would you use when they came back again? No, this way they won't bother us again" We never got bothered again - bloody pests!