Earlier quoted context omitted.
There's a tremendous amount of baggage in the loaded term "natural". But I think there might be a shred of reason to underlying the naturalistic fallacy if you interpret natural to mean "previously present in our evolutionary environment and therefore has previously exhibited evolutionary selective pressure on the development of our immune system and biochemistry." In other words, novel, isolated chemicals and proces…
That is a lovely hypothesis, but it has failed to stand up to testing. You go ahead and eat all natural poison ivy salads.
Your example likely demonstrates selective pressure within species--specifically urushiol in plants as a protective mechanism against herbivores. But you are arguing against the relevance of selective pressure. So you have beat up a straw man in which all things natural are better, but of course, I never argued that.
Do you believe in selective pressure? Do you think digesting cow milk conferred no evolutionary advantage? There ARE studies on the prevalence of the genes for digesting dairy milk, and I think they back me up.
http://www.nytimes.com/2006/12/11/science/11evolve.html?_r=0