Why would the Mormon church prohibit "hot" drinks in its Word of Wisdom? Because in the 17th, 18th and 19th centuries, coffee houses were the breeding grounds of free thinkers, dissention and revolution.
Why would the Bible say homosexuality was a sin while embracing male-dominated polygamy? Because a military and labor force can't be created if nobody's making babies.
By the way, can anyone direct me to where I can obtain a bumper sticker that reads, "My gay grandchild is cuter than your gay grandchild"....?!