Okay. Let's look at an old definition of "general welfare": The definition of General Welfare from just 40 years after the ratification of the Constitution:
Exemption from any unusual evil or calamity; the enjoyment of peace and prosperity, or the ordinary blessings of society and civil government (Webster’s American Dictionary of the English Language, 1828).
It is exactly this definition of "general welfare"--exemption from any unusual evil or calamity--that gives the government the authority to require manufacturers to adhere to basic product safety and quality standards, aka regulate them.
In this essay, "Enough Is Enough: Why General Welfare Limits Spending" by John C. Eastman of the Chapman University School of Law, general welfare is described as being of general, i.e. national, benefit, and that Congress decides what is a benefit. Under that definition, too, the power of the FDA to enforce nationally uniform product health, safety, and quality standards is completely constitutional.
Since you seem so against the idea of a national regulatory system, can you please explain to me on what basis you think having 50 separate state regulatory agencies doing the same function is preferable, and how is it preferable? (BTW, do not assume the states won't regulate--they can and do, in fact, regulate local matters.)
The Constitution was intended to create a national government of strictly limited and enumerated powers. As Madison explains, the interpretation of that clause you have chosen to embrace makes a mockery of that intent. It will come to no good, and before it's over with it will be doing it at gunpoint.
Again with the hyperbole! It is a pretty far stretch to claim that enforcing uniform health, safety, and quality standards is an infringement on our rights or freedoms. The FDA was founded in 1906, although its roots extend further back than that. It came about because of public demand following a series of incidents in which people were seriously injured or killed by using faulty products. I have *never* seen any situation in which the public widely demanded that manufacturers should have the freedom to sell them dangerous products. Realistically, it is unlikely, even unthinkable, that the public will take up arms over the practice of regulation.
I think it is instructive to look at the actual FDA guidelines/regulations regarding e-cigs and related products. If you read through it, you will see that the FDA is not banning these products. The page defines vaping products, gives instructions on how to apply for FDA authorization to sell these products, and specifies the legal limits of how businesses can market the products. And, for businesses or manufacturers who are confused by the process of getting their product authorized, the FDA directs them to The Center for Tobacco Products (CTP) Office of Small Business Assistance (OSBA), which will help them through the process. Once again, there is no move to ban these products--the effort is directed at making them safe and standardized--ensuring that you get what you pay for when you buy them, and that they won't poison you or explode.
What the Founders did, and every wound suffered and life lost in defense of it was wasted on you.