Please pardon me nitpicking on one phrase from your comment - it's not directed at you but at the discourse that often ensues when selective taxation is discussed. There was a soda tax on the ballot where I live last election season and I got more junk mail opposing it than
all the other political mailers put together - completely wasted as it passed anyway :)
I absolutely reject the notion that tax on soda or other potentially-addictive substances are a punishment of the consumer for poor moral choices. Making sugar expensive is simply an effective strategy to lower consumption by shifting the equilibrium point for consumer purchases.
We have a family friend that's disabled, she's an adult but only able to read around a 4th grade level. She's seen her grandmother die of diabetes, her mom has it too and the friend herself is fat. But notwithstanding the healthy food we give her when she visits or stays with us, and no matter how many times we remind her about how to choose between different kinds of food, if she goes into a store on her own and has money she's more likely than not to buy 2 quart bottles of soda and drink one of them immediately.
It's really hard for some people, especially kids, to resist getting jacked up on sugar. The younger they do so the more likely they are to develop lifelong eating habits that are going to give them painful and expensive medical problems and send them into an early grave. There's no moral component involved at the consumption end for me because many people are just not smart enough to carry around the idea of healthy eating and to choose it over the marketing signals that surround them. The younger they get exposed to an addictive substance, the more difficulty they're likely to have resisting the temptation to consume it.
I am utterly indifferent to the economic situation of shareholders in the crap food industry. They don't have a right to make money out of people; it's usually the suppliers who make the moral argument about consumers needing to make healthy choices and tax being a horrible punishment. That's just an attempt to shift the entire burden of responsibility onto consumers at the same time that the suppliers are spending a fortune on marketing to kids. Frankly most of the drug dealers I've met in my life had more of a moral center than the professional lobbying and marketing people I've known.