Always strikes me as weird when strong believers, people sworn to the service of God, learned in Bible and sworn to teach it to their congregation, decided that they know better than the One they respect above all.
Genesis 1:27
“So God created man in his own image, in the image of God created he him; male and female created he them.”
Or maybe if you believe so deeply in one unprovable thing, with its dogma and catechism, it is easier to transfer or widen that belief to another.