To me, forcing companies to print ingredients on labels subverts the free market. Whenever you pass a regulation forcing a business to do something, it requires enforcement of the rule. This means bureaucrats need to be hired, businesses need to hire lawyers to protect them from law suits and fines. Paper pushers are hired to file government reports. This rises prices as well as barriers of entry. And inevitably, bureaucrats clamor for more regulations, funds and power, and so do the established businesses, to protect them from the real check on bad business practices: competition.
If a company wants to print the ingredients on their products, great. They can do it, others don't have to, and let the consumers decide with their dollars which they prefer. I buy a lot of things from farmers markets and they have no label of ingredients, yet I think that their products are fresher and healthier than the same products at grocery stores with the products printed on the label.