How do you think you can talk to a theist about something religion based and have yourself not tuned out?
I talk about crazy 'versions' of bible stories and the person soon understands there is multiple versions of the bible. The Jesus screwing a woman who came out of his rib in front of Mary Madeleine on a hill which wasn't that big a deal because she travelled with him. Also the accusations against her were false.
I usually start with human/angel babies being the true reason for Noah's Arc. I don't claim to know everything and go at aspects in a non-shitty way. I talk about Corinthians is where covering your hair comes from and according the Quran Christians and Muslims are supposed to be brothers and both go to heaven.
I also managed to make someone think differently about sexuality and gender in this same fashion.
I haven't attempted to de-convert anyone and honestly don't know if I could. I avoid being tuned out by either listening or telling a story worth listening to.