About the cultural standards, what would be normal in some other parts of the world? At least in the US, parents don't want porn showing up on kids' social media, and a sizeable number of adults at least don't want other people to see it on their screen. Big social media site like FB probably has to encode this as a "no nudity" rule.

I'm not sure about the violent images. There are definitely rules against showing bodily harm on FB, but I have no idea where the line is.