I don't care what you want to put in your body. I expect the same respect from you.
Wow, you have a very carrying soul [/sarcasm]
Unlike you, the FDA has a statutory obligation to make sure that foods and drugs sold in the US are safe for their intended use. The "intended use" part allows for a surprising amount of wiggle room. How is the FDA to know if you bought vitamins to treat some disease (a drug use) or to make sure you meet the normal RDA (not a drug use)? They can't and don't try. The intended use limit is not on the end user, but the seller. VitaminsRUs cannot advertise that their vitamin pills prevent cancer, but if you believe they will there is nothing the FDA can do to stop you, and they won't even try.
You do not have the moral authority to tell another person what they may or may not ingest.
The FDA is not a moral authority, but a scientific one. They are staffed with experts in various fields necessary to decide which products are safe and effective, and which are not. You appear to feel yourself up to the task of sorting the wheat from the chaff, but most Americans are not. I'm going to go out on a limb here and guess that you consider yourself to be of above average intelligence and education (ironically, the vast majority of people do as well). But think about most of the people you see in a day (neighbors, friends, family, strangers). How many of them would you suspect are similarly equipped to handle sophisticated marketing made to give the appearance of scientific validity despite a demonstrable lack there of? That is why the agency was created (see patent medicines, most of which were simply different forms of cocaine). To protect the largely ignorant populace from unsafe and unproven products.
As I stated before: regulation to ensure the product contains only the labeled, unadulterated ingredients is the limit. I can also conceptually support banning "false claims" but that is a very squishy concept in biomedical terms and is typically advocated as an subterfuge to ban things.
All such regulations require oversight. Verification that companies are obeying the laws that are supposed to govern their actions. The dietary supplement market is exempt from much of this oversight because they lied to the US population and convinced them that the FDA was out to take away their vitamins and make they by prescription only. That would never have happened. I know this because I do regulatory work with the division of the FDA involved in regulating the animal equivalent to dietary supplements, namely Feed Additives. No prescription is needed for an approved feed additive, no consultation with a veterinarian is required, but feed additive manufacturers are required to prove that a new additive is safe and effective. Once approved, anyone can sell that feed additive for the approved use without further involvement of the FDA. A feed additive petition takes about 2 years (on average, with a HUGE SD due to a non-normal distribution) from submission to approval, but once the approval is made no more work is required. In most other countries the requirements are similar, except that approvals are vendor specific (Company A and B both have to register their Vitamin C), and have to be renewed periodically (US system only requires approval once).