The moral of (this particular) story is not that incest is okay. Actually it 's quite the opposite. It's interesting to see how Lot and Abraham are contrasted in Genesis. Abraham, although quite old, waits patiently for his promised son. Lot's daughters, on the other hand, have just seen the entire Valley of Sodom destroyed by burning sulphur. They were afraid that they were the last surviving people on earth. And so they plied their father with liquor and had sex with him. The daughters (not to mention Lot) had no faith in God. Hadn't the angels told Lot, and through him his family, that they were going to destroy the cities of the plain, not the whole world? So why this rush to incest? So Abraham's patient faithfulness contrasts with Lot's impatient faithlessness. Abraham and Sarah will have a son in their old age; Lot fathers two sons (who would become enemies of Abraham's descendants) through incest.
So no, the passage does not advocate incest. Rather, it uses the moral shock of incest to demonstrate just how bad Lot's faith was, in particular in comparison with Abraham's.
