I think the problem is the conflict between the two isn't symmetrical. Those who are trying to convince you to eat Coke and McDonalds aren't playing fair or accurately portraying what they're selling. and will promote research that indicates that lack of exercise[1] or fat[2], and will specifically advertise to children.
Comparing it to tobacco or alcohol for example, I don't think it's wrong to let people chose to consume them, but I don't think it's a bad idea to restrict them being sold to young people or restrict their ability to advertise. Imagine for example a cigarette ad for children. The tactics used are fairly similar.[3]