If Paul and Leviticus condemn it, it must be unnatural ;-). In this way, inspired humans determine what is natural and what is not, so the definition results in a very artificial meaning :-).

BTW, I am not entirely sure that "natural" means "good." I would argue instead that the natural aspects of humans are at once responsible for some of our worst behavior and at the same time the source of our greatest strength. But then I don't believe in the Fall from Eden either, and if I did, I would agree with the Mormons as to its moral worth :-)