I reject the natural/synthetic dichotomy. The natural/synthetic dichotomy is manifested in two fundamental ways: (1) the assumption that humans and/or human constructs are separate from nature and (2) the assumption that certain human constructs are "natural" while others are not. The problem with this dichotomy is that humans and their constructs are a part and product of nature; it is impossible for humans to step outside of the context of nature. Unless one wishes to posit a supernatural, all that exists or occurs is natural by default. Something that is not natural would be something that simply does not exist or occur at all. Hence, it makes no sense to speak of existing things or phenomenon as if they are not natural, or to defend or support a given thing or phenomenon by appealing to it being natural.
Everything is natural, regaurdless of how common or rare it is, when it occurs or doesn't occur, wether its beneficial or detrimental, good or bad, and so on. That which is natural, which is simply to say something that occurs or exists, cannot be construed as being good or bad by mere virtue of being natural. Nature is morally neutral in this sense, because the mere existance of a thing or phenomenon in of itself does not signify value. In other words, nature does not have intrinsic value. Understood broadly, it simply is what it is. This is not to say that there is no purpose or merit to assigning value to certain phenomenon, but that its mere occurance is not what gives it value. For if that which is natural is inherently good or bad, then literally everything must be assumed to be inherently good or bad, and that is absurd.
It's also important to note that just because something is natural does not necessarily mean that it is universal, inevitable or permanent. Nature is not static, it is dynamic, which is to say that it is in a constant state of flux. That which is common in the present may very well be rendered obsolete and archiac in the future. It can be quite fallacious to appeal to phenomenon from the past as if it is representative of an inevitable future or to regaurd current phenomenon as if they represent a permanent state of affairs. What once was natural can be rendered non-existant over time, and what once was little more than a pipe dream can become "the natural order". Appealing to the past as "natural" is simply a weak argument. The present and future is no less "natural" and the "naturalness" of things is really irrelevant.
One way in which the natural/synthetic dichotomy is manifested is in the arguementation of primitivists, anti-civilizationists and radical environmentalists. The contemporary technology and extended division of labor produced by humans is demonized as "unnatural" while more primitive and "self-sufficient" ways of living are romantisized as "natural". Human civilization is characterized as being inherently antagonistic with nature, and nature is assumed to have intrinsic value. Radically egalitarian philosophy makes use of the dichotomy as well, with egalitarianism being construed as "natural" while heirarchy is considered to be "unnatural". Interestingly, primitive societies are often pointed to as examples of egalitarianism, even though a non-biased look at such societies likely reveals quite a bit of heirarchy.
The natural/synthetic dichotomy is also manifested in conservative philosophy. Rigid class heirarchy, religious authority, familial authority, racism, nationalism, have been charactered as "the natural order" (with strong use of naturalistic language used to defend them), as if they are inevitable laws of nature and intrinsic authorities, and deviations from them are construed as synthetic attempts to produce a "new man" in antagonism with nature. Conservative philosophy strongly appeals to tradition as being "natural", and deviations from tradition such as homosexuality, secularism and multiculturalism are construed as "unnatural". All of this could be said to stem from a pessemistic and archiac accessment of nature that lies at the heart of conservatism.
Social contract theory and traditional statist apologetics is riddled with the natural/synthetic dichotomy because it tends to construe centralized political organization as if it involves man exiting "the state of nature", while at the same time there is a very strong temptation to characterize the rise of centralizd political organization as a "natural" phenomenon in the sense that is inevitable. Statism is construed as "the natural order" that inevitably arises from social organization. And statist politics is riddled with debate over precisely what kind of centralized political organization is the most "natural" or what the "natural progression" will lead to. Traditionally, anarchy is either brushed off as "unnatural" or is conflated with a primitivist "natural state" before centralized political organization took place.
While these various types of social phenomenon and organization most certainly can be evaluated, wether or not they are "natural" is really irrelevant to such an evaluation, because they are all "natural" to the extent that they occur or exist at all. The natural/synthetic dichotomy is a misnomer that sidetracks from the real substantive debates that could take place.