So, this topic comes to us courtesy of a recent op-ed in the NYT. I'd link to it, but when I tested the link it only comes up to a subscriber access page. Here's the gist. New taxes should be enacted on junk food to force people to eat healthier options. This will raise revenue and reduce obesity.
This, to me, is a frontal assault on liberty. It took a constitutional amendment to ban the sale of alcohol. Would it take a similar amendment to ban the sale of junk food? Maybe not with today's wide open commerce clause, BUT a wholesale ban would never fly. No one wants to vote on the next prohibition. So, should the government be able to do via the tax code what they couldn't do otherwise? Should they even be attempting to control what we eat? "But we have such a problem." You're absolutely right. We eat way too much junk in this country.
Shouldn't we be free to do so? Yes. Yes we should. Listen, if you tell me we should be free to suck a living child from a willing mother's womb but that the government should curb the eating of "undesirable" foods, then you seriously need to have your head examined.
If you want people to be thin, incentivize them. Allow insurance companies to charge "fit" people less than the obese. Quit classifying obesity and obesity related disabilities as qualified to receive SSDI, if after becoming fit they would still be unable to work. There are lots of ways to go about this, that don't involve the government mandating anything, either directly or through the tax code.
The broader question follows the same logic. There are ways to create the goals of many in the government, but they rely on hard work and the ability and freedom to try and fail. Just as the government shouldn't treat any one business as to big to fail, neither should they treat any movement as too big to fail. You don't need new taxes to promote a concept and influence behavior. Free the Market to do it instead.