Dangerously Sinthetically Natural
Let's gloss over the moltitude of natural yet noxious, intoxicating if not deadly substances (capsaicin, jellyfish venom, ethanol, morphine, ricin, amatoxins and many more) for pity's sake.
Lately, the group touting this belief that came to my attention is soap/cosmetic homemakers. I personally have nothing against makin this stuff at home, but I'd really like if those who want to spent a bit of time studying basic chemistry first, before reading manuals that perpetuate the misconception.
Instead, I had to develop a product that meets some objective standards of toxicity, and to achieve that I did my research. For example I found a ponderous document prepared by some EU agency, according to which fatty alcohol ethoxylates - a class of non-ionic surfactants - are about as benign as they can be to humans and environment. Yet according to natural detergentmakers, anything ethoxylated is evil.
There is also an issue of effectivness for natural detergents. Sodium and potassium salts of fatty acids - that's what soap is made of, and it is not that natural either because it is manufactured by alkaline hydrolysis of lipids - are not that effective as detergents. Their limits lie in their very chemical structure, and nothing can be done. That's also why more effective chemicals have been developed (by contrast, the iron-based catalyst used for ammonia production has not changed much since it was invented, because it is effective, relatively cheap, strong and durable).
Chemicals approved by natural enthusiasts appear to be alkyl polyglucosides. Which are nice and renewable ones, sure, but still the product of industrial chemistry; they don't come out of plants as they are (at least in significant amounts).
Another website I saw says that caustic soda should not be used for biodegradable formulations, while sodium carbonate is ok. Oh boy... if you're so deficient in basic chemistry, you'd better stay the hell away from preparing stuff that will come in contact with your skin. Well, if the issue is safety during manufacture, then I can agree sodium carbonate is less dangerous. But biodegradability... sodium hydroxide will react very rapidly with a number of chemicals and thus be destroyed. Unless we're talking about an industrial-size spillage of soda, there are no major problems. And sodium carbonate is the same in this regard. Moreover I suspect that often sodium hydroxide is used as part of a buffer system to control pH of the formulation (we're not talking about heavy-duty industrial degreasers here, but personal care products).
And is sodium carbonate truly a deodorizer? Yes, it can be. It can hydrolize ill-smelling compounds, but mostly it will help to bring into solution the ill-smelling chemicals of acid nature - such as rancid oil. Ammonia will do the same, for example. But ammonia is not nice; surely less than most artificial or synthetic surfactants.
And so on and on, I could make many more examples. My take is use as little as possible of the best chemicals for the job, and be careful how you use them.