Nudes are fine. All you puritans and prudes... lighten up! I agree 100% with JBrunner that only minds are dirty.
As for David, anatomically (especially his back) there are quite a few anomalies — artistic licence combined with exaggeration of anatomical form.

Sadly for David, he was looking considerably worse for wear after a 2-year loan to the Guggenheim. They won't be doing that again. Take your pick which is the most beautiful nude.

David after 2 years on loan to the USA.png