In a way I agree...

I don't think art should be a defense. If (and only if) a child is actually harmed in some way in the making of a picture it should be a crime, art or no. Of course we know the law doesn't require any real harm, but still on principal I don't think art should come into it. And personally, as an artist, I wouldn't be very comfortable knowing that my right do something was contingent on someone else's judgment about whether it was artistic or not.

"Obscenity" (but not child porn) in the US is the same way. One of the exceptions is "artistic merit", but like I said I'm profoundly uncomfortable knowing my freedom could rest on something so subjective. In the long run, we might be better off without these exceptions. Then people would be forced to confront the issue head on and decide whether the law is just or reasonable to start with.

I may well be overestimating the intelligence of the common man, but I think a few notable artists getting thrown in the slammer would make an impression on people.