Regardless of our choice of food type, current levels of demand require monoculture of plants, which cause substantial disruption to the environment. This disruption means the suffering and death of wild creatures either through loss of habitat, starvation, pest control or through lethal contact with farm equipment. If all humans stop eating animal products, we will have to dramatically increase the amount of horticulture to meet our need for food - and in horticulture, we have little control over the suffering of competing species.
While we have little control over animals competing with horticulture, we do have techniques available to reduce suffering in animals that we raise for food, provided we study them from a scientific perspective and not an anthropomorphized one. It is important to note that while farming techniques might need improvement, farmers are often unfairly branded as "inhumane" by laymen for techniques scientists have found are not bothersome to animals (see foie gras, for a controversial example.) It is also important to note that ovo-lacto vegetarians cannot consider themselves more "humane" than meat-eaters, since an integral part of raising cows for milk and raising chickens for eggs is the slaughter of bulls and roosters.
We are a species that consumes and competes with other life--there is no single choice of diet that eliminates environmental impact and suffering. I would argue that the most ethical diet is one that minimizes overconsumption of resources and reduces waste as much as possible; which genre of food we choose is less important. I would also argue that the main difference between an omnivorous diet and a vegan or vegetarian diet is that omnivores can directly quantify the number of animals that are slaughtered for consumption, but we have no direct way to quantify how animals are impacted by mass horticulture. I would further argue,then, that veganism and vegetarianism represent a symbolically sympathetic relationship with animals, rather than a quantitatively positive relationship, and as such do not represent a more ethical diet.
If you put a man and a wild tiger in a cage together, there are only two possible outcomes: the man kills the tiger or the tiger kills the man. The only difference in outcomes is that the tiger sees the man first as prey and second as food, and otherwise does not think about the man at all; the man may have many different reactions to the tiger: fear, awe, compassion. Looking at animals from an ethical perspective means that we are using a very human yardstick to measure something not at all human. In my opinion, our obligation to animals is less about their experience and more that they provide a lens through which we can learn about our own behavior. Animals can teach us to avoid actions that increase our propensity for cruelty (e.g. dogfighting), even as we learn to humanely grow animals for food.
UPDATE: My response to the six finalist entries. This isn't sour grapes: I concede that my arguments may not have been the best out of thousands, but at least it's an argument for eating meat, not a backdoor argument against it.
Is it ethical to host an ethics contest for the purpose of showcasing your own position?
Earlier, I wrote to the NYT with a concern that the panel for this contest was biased. I suggested that, to address this bias, they should recruit someone with a background in agriculture and an understanding of the science behind raising animals for food.
The six finalist essays show that my concerns were well-founded: all are more or less against meat-eating; none of them meet the initial challenge presented by the Times. I find it hard to believe that out of "thousands of entries," these six essays present the best reasons for making meat a part of one's diet.
If the New York Times wants to promote a vegan, vegetarian or "flexitarian" diet, it should just come out and say so.