Law is never perfect

In a sense I agree that the artistic defence is a recognition that Law isn't perfect (ie, that censorship by the letter of the law would inevitably go too far) - but it also introduces a far larger subjective element in the application of Law (what is too far?).

Ideally, no image (or sculpture, or performance, etc) should ever be illegal in and of itself - although the producer should be liable for any other offence committed in order to produce it - which would include sexual abuse, if applicable. The problem is that some people, which includes activists, lobbyists, politicians, lawmakers, lawyers, prosecutors and judges, still believe that content itself should be prosecutable lest it encourage copycats to engage in the illegal acts that were part of the production.

Of course, as long as kp images are deified, we're gonna be very far from the point where a work is legal even if the producer is prosecuted for offences committed in order to make the work.