From a legal perspective, what I or any other individual consider as the boundary between art and pornography would have zero bearing on your friend's situation.
I think saying that art and pornography exist on the same dimension is not correct.
There is art and some of it uses the attraction and tension of sexual desires to produce feelings in the viewer. The more uncomfortably close these feelings get to the 'edge' for that viewer, the more successful the art is seen to be at arousing emotion and pushing boundaries.
And there is pornography which is aimed only at exciting the sexual interest of the viewer - and the art in it is not the primary intent but is useful to make the pornography more enjoyable by diffusing some of the less visually attractive aspects of what is being seen.
It is where these two arcs intersect that is arguable.
When there is something that is damaging to the individuals involved, then the state has a compelling interest in drawing a line..
When the individuals involved are too young or are otherwise incapable to chose to be involved or not, then the state has a duty to protect them and must draw a line that may be aimed at pornography but also intersects that of art because the duty of care is to the subject and not the intent of the artist.
So. while an adult can chose to be branded for art's sake, you can't torture either rabbits or children and call it art because the state has a duty of care to both.
In the case of child porn or art, the damage is so important that the mere fact of possessing these materials encourages the creation and the damage.
This is a similar concept to the banning of the sale and export of ivory and the ownership of protected exotic species.
In regards to one's personal feelings.
In the movie, 'the African Queen', Humphrey Bogart attempts to explain away a vice by saying that it is only human nature. Katherine Hepburn replies, "'Human nature is something we were put on Earth to rise above."