I'm not losing any sleep over nipples one way or the other, but it never ceases to amaze me how violence gets glorified in popular culture while simple body parts can be so stigmatized.
I heard Will Ferrell talk recently about movie ratings. Anchorman 2 was trying very hard to get a PG-13 rating, but getting tons of grief from the MPAA about some poopie and dicky doo type jokes. They had to cut a lot of stuff to get the PG-13. Meanwhile, the Hunger Games movies are filled with graphic images of children murdering other children for sport, wrapped up in some very adult themes of oppression, fascism, mass murder, etc... And Hunger Games had no trouble with the MPAA and gets the PG-13 rating.
I know this argument gets brought up all the time and has become a cliche, but there's something very important there. A lot of people have a lot of weird fear and repression about not only sex, but the human body.