It really is - we're talking about economic incentives and there are economic incentives for poor people to buy soda (it's cheap) and for large companies to sell soda (it's inexpensive and high-profit). The way to handle this is to make it more expensive to buy (taxes - which are regressive, as cgod pointed out) or more expensive to produce (end subsidies).

On the local level, municipalities can pass whatever stupid taxes they feel like. My home town tried to fine people for the amount of dogshit they had in their back yard until someone asked who the fuck got to enforce it (let alone weigh it). But dealing with national issues such as our 50-year history of subsidizing corn production is far beyond the ability of your average hippie town to attempt. The end result is local attempts at national problems.

That national problem is a dearth of nutrition. cgod is all about individual responsibility but at the end of the day, if there's more money in Coca Cola than there is in spinach I'm going to have a devil of a time buying spinach and an easy time buying coca cola.

Ain't nobody saying you can't buy soda. But if your soda habit means you're more likely to have diabetes it means that insurance rates go up which means your soda habit directly impacts my quality of life. It's a problem of externality.