Yeah, the word is often used in a supportive way in argument - something is okay and understandable because it is natural. But "natural," used in that sense, can be used to describe anything that occurs in nature.
I wonder if the people who think rape is natural (because it occurs in nature) would be willing to say that male gay sex or bestiality is also natural because it occurs.
I don't know. What possible phenomena can occur that can be called unnatural? 'Natural' is as meaningless as 'organic.'