I was going to say something similar to damned_colonial. Some vegetarians avoid meat because they think the consumption of animals is immoral. Really they think the slaughter of animals for food is immoral, but as consumption necessitates slaughter, I don't know that it makes sense to consider the moral value of the latter without the former. I think I get what you're saying, though: there's nothing moral about the nutritional content of food (or the lack thereof).

I have to ask, though, do you think people genuinely ascribe a moral value to foods? If one has a salad for dinner and another person says "how good of you," I don't think it's meant as a moral judgment. It's praise for the wisdom and willpower of one who opts for a healthy meal when something less healthy might be more immediately satisfying. Similarly, if somebody eats McDonald's every day and I say that he shouldn't do that, I mean that he's making a bad choice and will suffer for it; I don't mean that he is an immoral person. There are other standards besides morality by which a choice can be judged. In this case, I think most people use standards of healthiness (real or perceived), not morality, to judge what is a good food or a bad food.