I was an avid vegan for seven years. Even worked at an animal sanctuary as a tour guide and tried to convert people. I now see instead that I was ideologically possessed, and moral veganism is unfortunately tied up with a profoundly anti-human sentiment. Discrepancies are overlooked with dramatic eagerness because veganism is, without exception, deeply tied into the identity of any given vegan, myself included.

The problem is your question. Specifically, the collective-grouping of thought-forms that produces that question in such a way to make people ask it without realizing that it says much more than it does. More specifically, what the question entails: that death is bad, that unnecessary things should not be done, that humans should not do things they do not have to, and that veganism is truly as healthy as a good omnivorous diet.

"Killing is wrong" is a pretty recent staple of society, historically speaking. It's also easily observable as untrue, at least in our extant choices and actions. It's built on the idea that death is bad. In veganism, it goes further to posit that animals have a vested interest in not-dying, something not demonstrably true and extraordinarily unlikely. There are marked differences in human and non-human animal cognition which can be empirically observed. That's the field of behavioral psychology. Animals are not aware of death as an abstract concept. That death is bad is exclusively human, and particular to our culture. That life is good and should continue on is, similarly, exclusively human. That we use these words which only exist for human beings to explain animal behavior is a result of our projective psychologies, not any objective reality.

Just about anything a given human being does is unnecessary. We do not actually base our behaviors on whether they are needed or not. They're a series of pleasure-seeking pain-avoiding behaviors with complicated psychological factors which sometimes result in strange contradictory actions. To evaluate something morally on whether it is necessary is a direct path to fascistic thinking, only thinly veiled. You may notice that many vegans are fond of rhetoric which: describes humans as a cancer on the earth, insists on the necessity of population control, expresses desire for environmental catastrophe for the perceived benefit of lower population and lesson-teaching, shows general disdain for other natural human activities like reproduction, shuns technological developments, shuns scientific data in favor of emotionally charged argument, etc. This is that anti-human sentiment I alluded to. Humans do not exist to do only what is necessary. I assert that we exist to explore, press boundaries, thereby creating and overcoming problems. We do not exist to treat ourselves as if we did not have a right to the resources of this planet. We are not aliens here, and nature made no mistake in our creation. There is no intrinsic value to the life on earth as it once was, and no amount of bitterness toward our species will stop us from being the way we already are.

Veganism is, in general, a very healthy diet. Healthier than a healthy omnivorous diet? Almost certainly not. Healthier than most standard diets in the world today? Absolutely. Dramatic but easily-correctable vitamin deficiencies aside, nutritional science is relatively new. My personal experience has been that, after 7 years of no-meat, my clarity of mind and mood improved dramatically after reintroducing meat into my diet. That is despite the absence of any nutritional deficit. Veganism has yet to be clearly challenged against healthy omnivorous diets, and the research that does exist is not promising (for veganism). Many of the health claims vegans make about various meats are not only misleading but downright false.

It is not the responsibility of the extant behavior system to justify itself. It is reality. It is what is. It is the result of hundreds of thousands of years of slow changes, adaptations, and abstractions derived from our existing behaviors. If you want to change what is, it is your responsibility to explain why. It is also your responsibility to explain why in a frame which remains relevant to the extant reality, instead of creating a false dream-land for yourself where specific self-defined compassionate ideals are necessarily imbued into nature and goodness.

If I were to rewrite your question, I would ask: Why should humans stop doing a pleasurable, efficient, and healthy activity in the interests of another species? What are the interests of that species or its individuals and why do they entail that we should not take advantage of our superior position? Why do other species without nervous systems not get the same consideration, when they presumably have the same evolutionary-derived interest toward continued life?

I think there is a very clear argument against factory farming and animal abuse in all forms. "But killing an animal for food is murder!" No, it's not. As I mentioned, we use human words to describe inter-species phenomena, although they are misleading about the equivalency of the experiences of the two beings (or types of beings) in question.

I also think there is a clear case for eating less meat than is common in American society, at least. As well as eating a greater variety of fruits, vegetables, and fungi. But the health angle for veganism is actually relatively weak with careful examination. I am ashamed to admit that somewhat, as I used to be rather militant about how obviously better it was.

Too, the environmental angle is very strong. Here, I am skeptical as well though. Despite popular narratives about certain impending doom for our species and the life-web of the planet, there is little objective likelihood of such an outcome. The earth is an adaptive organism and we are a capable and adaptive species. As with the health side of veganism, there are alternative narratives which are usually dismissed outright without consideration. That dismissal does not mean they are invalid, however, only cognitively dissonant with your current cultural-political programming. That does not mean they are true either, only that they are worth considering as an exercise in understanding just how little we actually know.

But when I adopted veganism, I adopted an entire state of mind. An anti-establishment, governmentally paranoid, anti-human state of mind. I had no idea I had done so. It was just already part of the social group I integrated into. Veganism is religious - that's not an exaggeration. I've been looking continually for a moral justification for veganism which does not rely on false equivalencies between human and non-human animal experiences and it simply does not seem to exist. I cannot create it in myself. The pointed-to founder of explicitly theorized moral veganism (Pete Singer) is the worst perpetrator of of that equivalency. Moral veganism requires the axiom that "Human and animal experiences are comparable to such a degree that we do not need to distinguish between them." This is clearly demonstrated in the nonsensical comparison of speciesism to racism. Species has a clear utility in prediction and analysis - it is a useful part of reality. Race does not. You can accurately predict an organism's ability based on its species, but not on its race. Vegans are generally completely unaware of this very unsteady pillar of their belief system.

I don't write this to discourage you from going vegan, only to provide some topics for thought. My hope is to prevent complete ideological takeover. Change your diet, sure. Believe it is the objective, unassailable truth about how humans should live? Probably a bad idea. For all the open-mindedness vegans believe it takes to become a vegan, we seem to abandon that value completely once we have entered the echo-chamber of righteousness. The fact that your average human is not able to articulate abstractions for the reasons for their regular behavior does not necessitate that there are not good or valid reasons for that behavior. Please do not mistake your chosen moral values for absolute facts.