Personally, I don't believe in morals, because most "moral values" I know about are vague and "true just because they say so".
Don't touch a hot stove.
YOU CAN'T TELL ME WAT TO DO!!!1!
* burns hand one or more times until the pain response prevents further hand-burning efforts *
Morals aren't a source of authority, they are a shortcut, a table-of-contents entry into an encyclopedia of experiences.
Morals are a form of optimizing behavior patterns to the environment in which we exist.
In the Frontier days of the 1800s, there was value in breeding large families; expansion to fill the Wild West. And the Industrious Man who earned his keep through hard work was a valuable asset at that time. So the Book of Mormon, which was written at that time reflects that specific set of values. But it's frozen in time, and thus a bit out of date.
The world of the 2000s is full of people, and so large families are no longer as valuable as they once were. So the morals of the day are fear of sexual intimacy, homosexuality, and anything else that slows breeding.
Just Say No To Drugs. Smoking is Evil.