I know we should change from within and think for ourselves about what's healthy for us and what's not. However, what's wrong with cheaper healthy food and more expensive bad food? This sounds like a win-win to me. Healthy eating people will have to pay less and others will get to think twice, before continueing their unhealthy habbits.
There's also the fact that not everyone has the money to spend on a healthy diet, because this healthy diet can get pretty expensive, as opposed to an unhealthy one. Sure, water from the tap is much cheaper than all the soda being consumed, but overall, healthier food seems to be more expensive. A bag of chips is cheaper than having an equal amount of tomatoes, cucumbers or bell peppers to snack on. Want to snack on some unsalted nuts? You get to pay thrice (or more) as much.
A valid point, certainly in some situations. The locally sourced organic veggies at my local food co-op are often double (or more) the price of "regular" veggies at the supermarket. Leaving the dilemma for more than a few of whether you "starve healthily" or "eat unhealthily."