To a theist, all things are the creation of god. There's no argument that can't be settled as "god made it that way". The real place you gotta hit em is in the arrogance of believing that the almighty created the bible, not humanity. And if they say that a sentient entity willed it thusly, then we return to the problem of evil: if humans are capable of evil, and this is god's will, then the benevolent god in the bible is not accurately depicted. I wonder what else the bible got wrong? Maybe their god willed the creation of a bible that got stuff wrong on purpose?

Honestly, for a dystheistic spiritualist (that is to say, one who believes that the greatest ordering forces of the universe are neither good nor bad nor have any intention for us, yet recognize the importance of spirituality in human livelihood) who is conversing with a bible thumper, this is the best you can do. Help people depart from their idols and attachments, and connect with the real human experiences of the spiritual. The less we get distracted with rules and traditions, the more we can love our world and one another.