Here's an interesting article on the subject of Nudity and Censorship online: http://nudistnaturistamerica.org/nudity-and-censorship-online
Let’s take a look at Facebook. The way that Facebook censors nudity for its 700 million users is odd to say the least. Images of mothers breastfeeding their infants are not allowed if nipples are showing (even partially). Male nipples are considered to be acceptable, but a female nipple are cause for alarm. The dividing line between what is considered acceptable and what is pornographic is not clear. oddly enough, gore and violence are perceived as acceptable and harmless.
Read more in the original via the link above.