There are several inter-related elements entangled here, several of which have strong emotional, moral, and legal content.  That makes it extremely hard to talk about any one element in isolation.  As much as you try to speak about a statistical study on facial attractiveness as reported by test subjects in Germany, one of your listeners is going to see it as an argument for or against some form of censorship, forum moderation, artistic nudity, pornography, or real-world sexual activity.

Morally, we recognize that if art is to be meaningful it must be kept free of censorship whenever possible.  To limit what can be said or shown is to limit what can be thought, and it is on that cutting edge of thought that art validates itself as more than just entertainment.

But there is also practicality.  I'm in theater; we're all about practical.  As much as, say, Renderosity might wish to avoid censorship, a certain amount of self-censorship is necessary and smart in order to keep themselves out of trouble and keep the site open for as many works as possible.

Morally, we recognize that brain development and social development lags behind sexual development, and that children will be physically capable of activities long before they are emotionally or socially ready for them.  This is not just sex, of course.  With help in reaching the pedals a five-year old could drive a car.  No-one in their right mind would give them a license, however!

Our genetic history makes it so what appears to be fecund will cause a hormonal reaction.  This instinct lies outside of our socialization and intellect, but how we act upon this instinct is fully controlable by socialization and intellect.  But we would be foolish to pretend the original reaction is not there.

Thus a problem in the real world, where just like instincts to use fists to settle arguments, or to eat handfuls of processed sugar, the sexual instincts must be channeled into channels appropriate to the society's goals and the well-being of all the individuals involved.

Complicating the issue of "pornography" even further is that the viewer brings their own baggage to a scene.  For a foot-fetisist, a full-page advertisement for a bunion treatment may be pure-quill porn.  There are very few people that would disagree that a portrayal of naked people in intimate contact is not meant to be taken sexually.  But, scarily, quite a bit of what is traded as pornographic material online may have originated as, and to outsiders to that particular fetish likely appears, quite innocent pictures.

And then we have the virtual world.  Where we are creating shapes that have not existed before.  One could argue that way back as far as primitive fertility figures artists have been able to create breasts too monstrous for a real woman to carry.   Certainly, the traditions of anime have built upon the original Disney inspiration, and the cult of cute already endemic in the culture, to create legions of depicted creatures with elements not present in any physical body.

As the German study emphasizes, we are able with technology to provide for our senses something more saturated than the natural world ever produced.  Purer colors, more processed sugars, purer sound colors, and faces (and body shapes) that have more of  a kick than what the real world has provided so far.  (And, like the processed sugars, such things also pall quickly, leaving us a desire for more complex and nuanced tastes.) 

Easy answers?  Simple solutions?  No.  In fact, on the narrow subject of age play alone there are raging battles going on in several corners of the internet.

All we can do as individual artists is to recognise the existence of all the issues involved.  And that means being prudent.  Although your intents in creating a certain image may have been wholely innocent, it benefits you to look at your own work with the most narrowed of suspicious eyes.  Could there be a narrow-minded parochial judge, or cop, or teacher, or employer, who would see in that image something you didn't mean to put there?

Look.  Look for trouble.  And then make your own descision on that image (or product, or essay...), balancing your need for artistic honesty against the need for self-preservation.