Most countries dont have a problem with nudity/human nation. American values have always been a bit different than asian/europeans though. I personally dont think nudity/nakedness should be ashamed.
However, sex and nudity are two TOTALLY different things. Sex for A LOT of people is something SACRED between two people. Fucking with anything "sacred" is NOT a good idea. I understand for some, it may just be a beautiful natrual thing, but for others it is something that SHOULD not be portrayed unless in the proper enviroment.
As for violence, I dont think violence is pretty, but it is in our nature. Jealousy, anger, rage, coldness, they are all part of humanity. The most extreme cases of these evil aspects are portrayed in violence. For most Americans, it is also entertaining, due to the amount of polar-drama that violence USUALLY carries.
I personally dont mind violence in movies and I understand itll happen in real life. It is human nature. As for nudity, a body is a body is a body, I dont see teh big deal. Sex I can understand why some may get upset, but if they DO get upset, most of the time it is avoidable. If it is in the public, it is illegal, and they can have them arrested if it is unavoidable.