This post argues against veganism and in favor of the consumption of meat and dairy products.
The moral argument for eating meat and dairy products is simple. If we eat them, we contribute to the economy that gives these animals life. Since their lives have value to them, it is better for them to exist than to not exist. And also, if their lives have no value to humans (for food or other uses), then these animals will cease to be so numerous and will probably become extinct.
The moral argument for veganism is generally based on not killing. But if we don’t slaughter cattle for food, soon there will be no cattle. Veganism, to put it strongly, is arguing in favor of cattle genocide.
The vegan argument is based on the belief that the animals’ lives have value to the animals. If the animals themselves did not want to live, the vegan argument would not be strong. But if we accept that the animals’ lives have value to them, then raising them for meat or other uses benefits the animals as well as humans.
The strongest argument for meat eating asks that the animals be treated humanely while alive and slaughtered humanely when the time comes. But even if the treatment and slaughtering of these animals is not perfect, it can still be reasonably argued that it is better for them to have existed than to not have existed.
An argument for limited humaneness—that is, “just humane enough to make their lives worth living to them”—does not appeal to me but is probably sound, though clearly it is morally weaker than an argument for greater humaneness.
An objection to this overall argument might be that it is somehow wrong to raise a sentient being knowing that you intend to kill it. But when we take a pet into our home, we all know that the chances are we will kill it when it becomes too infirm to continue. Many people, myself included, argue in favor of euthanasia and even suicide for people who have reasonably concluded that their lives are no longer worth living.
When and if we have widely available lab-produced fake meat that involves no killing, would it still be morally right to raise animals for slaughter? My answer is yes and for the same reasons—those animals are being given a chance to exist and it is better for them, from their point of view, to exist than to not exist.
To some extent, the above arguments appear to support the Buddhist Theravada position that lay Buddhists can eat meat. And that monastics can also eat meat if the animal was not killed for them, if they did not see the animal being killed, and if they did not kill the animal themselves.
The Buddha ate meat and made these rules for monastics and himself. Mahayana Buddhism developed a vegetarian tradition because mendicancy was not feasible in China and other northern areas. Indeed, Mahayana Buddhists who consume dairy products and/or eggs are actually participating in industries that slaughter animals, for dairy cows and chickens are slaughtered as soon as they cease to be productive.
Based on the argument presented in this post, Mahayana Buddhists are right to consume dairy and eggs and wrong to eschew meat if there are not other factors (health, personal taste, environment) being considered.
I have not covered environmental factors in this post because they bring in many other considerations that distract from the basic moral argument.
As for fish, it seems to me as of this morning that eating “wild caught” fish is not morally well-supported because our eating them does not support their existing. Wild fish would be better off without us eating them. Farm raised fish and hatchery fish, of course, would be better off existing before being slaughtered in the same way that beef cattle are.
American Buddhist Net 
I doubt if many Alaskan indigenous people would still exist if they didn’t eat meat.
“An objection to this argument might be that it is somehow wrong to raise a sentient being knowing that you intend to kill it. But when we take a pet into our home, we all know that the chances are we will kill it when it becomes too infirm to continue.”
A difference is that animals raised for meat are killed not when they have grown old and infirm but in what would otherwise be the prime of life, were they not being raised specifically for slaughter. It makes sense for now, especially since viable alternatives do not yet exist, to argue that meat animals have been given a chance to live and better a short life than no life at all. But at what point, if ever, does the human-determined fact of their very short lives become at least a factor to consider? It was humans who made these breeds what they are, who in a sense created them, and perhaps this gives us some authority to speak “from their point of view.” But what would they actually say if they comprehended their situation (assuming they don’t already) and could speak about it? They may very well say that they’d enjoy living to middle age and beyond as companion animals do. Should this be taken into account? Perhaps I am speaking less to the question of should these creatures be perpetuated beyond the point of strict necessity and more to that of how and in what numbers.