i'm pretty sure that the justification is that the site also caters, in part anyway, to underage people.
Now I'm even further confused. Why does a site that has forums for "Free Love", "Bare It", "Genitalia" and on and on, also cater to underaged people? Just curious.
i don't know how they decided the age limits. when i first started here you just had to be 13 to sign up. and back then, there was all kinds of nudity. at some point they raised the age to 16 and got way stricter on the nudity rules, saying that because people under 18 were allowed to join they weren't allowed to have anything that could be considered pornographic on here. i guess they're just trying to make the site relevant to the greatest number of people.
the desire of humans to live in cities, to indenture themselves to personal motor vehicles and then drive them in cities and only in cities, to live in rectangular architecture and demand that other humans do the same. (and prefer the accumulation of symbolic value to things they can actually do anything with and enjoy doing so)