It comes down to individual tastes... But even that is heavily influenced by the society you were brought up in as well.
For example, Western Cultures, specifically, the U.S., has a fit about nudity thanks to our Puritain roots... Yet we have no problem with senseless violence where fifty thousand people can be killed (on screen) in the name of "justice".
What is more natural? Seeing a man's schlong or a woman's nipples...
Or seeing portrayls of people being gunned down, blown up, burned alive, blugeoned to death, etc -- Which, by the way, is now considered "PG-13" material and completely hypocritizes this whole obsession with what is appropriate and what is offensive in my opinion.
Actress Jamie Pressley said it best: People in this country [USA] make such a big deal over nudity and its about time they just get over it because it's not that big a deal in Europe and other places. Who really cares?!
It should be noted she is from the South which is very conservative in a lot of respects as well.