That aside, I can name several ingredients in flavorings and coloring that have proven health risks when it comes to inhalation. Diacetyl, used for butter flavoring is a biggie that causes permanent lung damage, often referred to as "Popcorn lung". Diacetyl substitutes have been shown to have similar toxic effects. Many bakery flavors and some candy flavored eliquids will include either diacetyl or one of it's substitutes. For example, you can't make a really good toffee or custard without a little butter flavoring.
These are proven health risks. It's much easier to ban ecig use than it would be to ban using specific flavors unless you give the police the right to take your ecig and have the liquids tested.
Actually, the diacetyl scare was because 30 people got popcorn lung. 29 of them worked in a popcorn factory (or some other similar factory - don't remember exact details now). I also read that all (or nearly all?) of them were heavy smokers. Cigarette smoke contains diacetyl, in higher concentrations than found in vapor.
So millions of smokers have been inhaling diacetyl for years, but no popcorn lung outside of the industry (except that one - and I don't know details). No popcorn lung in a vaper (yeah, I know, it takes years, but still...)
Once I'd done the research, and realized how miniscule the risk is (I have a better chance of being struck by lightning!) I decided diacetyl was a non-issue for me. And as far as 2nd hand vapor, studies have shown that there are no detectable levels of anything dangerous.
So again, I say prove the harm BEFORE you ban something. In the case of vaping, they cannot prove harm without cheating.