Justin S. said:
It's generally best to avoid "natural". It opens more debate and questioning rather than achieving resolution. The same applies to some outright rejection of it (ie 'its merely a social construct'). Even if it were possible to determine what exactly "natural" would be in each context, it would lack any value judgment, as this process comes after acknowledgement of a phenomena (and most certainly is a "construct"). Another issue: if everything that is is natural, than we have said nothing, and the criticism of "unnatural" meaningless.
Norsemaiden seems to suggest some belief in the "progression" of evolution, rather than a "state of affairs". Again, what is is, value judgments are distinctly separate. As soon as we claim goals, purposiveness, and rankings of worth in the unfolding of the universe, we enter irresolvable games of metaphysics.
Rather than grasp for the Truth(tm) of some "objective" ground, much more convincing arguments can be made by discussing relationality. What relation does a thinking, acculturated being have to art, to imagery, to death, to gore, etc. What motivations would prompt them to display it in such and such a way. Through this process one can find much more damning, grounded, and particular evidence for the ignorance of "gore-lust" than by accusations of violation of "natural laws".
All valuing in this manner is deeply flawed, but that's too broad of a topic for now. Needless to say, the problems of defining "natural" apply to the other terms found in this thread (sanity, sadism, etc.)