Is a high-salt diet good or bad? Is it even possible to achieve a diet with a specified level of salt? (There is some evidence that almost all humans on earth have very similar levels of salt in their diets--regardless of diet). Has fast food given us a high-salt diet that is bad for us?
Amazingly, there is considerable doubt about all of these questions--the science, we might say, is unsettled--but that hasn't stopped a lot of people, including public health people in government, from pontificating, and even imposing regulations. (See also here and here).
The various food scares, most of them discredited sooner or later, have done a lot to discredit the whole idea of public health advice from government. (Then there are the viral epidemic scares--a whole different story). I think climate change is likely to end up the same way: people who claimed to be experts, giving us advice for our own good, turn out to be pursuing some other agenda.
By the way, I would just add to this piece that there is some question as to whether obesity is bad for us. Again, another story; see here and here.
Here's another example: the argument that even a residue of cigarette smoke on an adult's clothing is harmful to children has been widely promoted, and even formed the basis of government policies on adopting and fostering children.
But, er, there's no actual evidence to support the claim, and the evidence that does exist suggests it's highly unlikely.