Unintended consequences of arguments other than animal ethics
The ethical argument for Veganism will always be the strongest and most consistent to use in Vegan activism. While there is a significant amount of merit to the environment, sustainability, health, and even economic arguments (possibly even theological, if you know your audience), for the average person living in a modern, first-world nation, there are no real counterarguments against ethics that are worth considering.
We strongly encourage Vegan activists to primarily focus their activism on ethics since it's more bulletproof than any other argument, but it's also incredibly helpful to highlight the other arguments in favor of it, which provide even MORE reason for a person to go vegan, but also highlight the lose-lose nature of animal agriculture, in how it also hurts humans instead of just animals, and that there aren't any real positive of it that negate the benefits of veganism.
This article will not be discussing the consequences of using bad arguments in favor of Veganism. The problems with those arguments are much more obvious, including making Veganism seem like it isn't based on evidence and reason, making it hard for people to justify their veganism, and on top of that, giving anti-Vegans ammunition against the movement. It will more go into how using otherwise valid arguments irresponsibly can have some negative repercussions that can be counterproductive, including misrepresenting what the science actually says, to possibly cause people to eat more meat if there isn't any strong ethical argument.
Environment
The environmental argument is probably second to ethics in terms of strength, but since it's more of an empirical claim, it lends itself to be misrepresented a bit more rather than arguments from ethics (which are based on logical reasoning). Specifically, a common mistake many Vegans make is claiming that most, if not all of our environmental and sustainability problems are primarily caused by animal agriculture, such as claiming that it's responsible for over 50% of emissions, or claiming that it's the main cause of world hunger.
There is no arguing that if more people started consuming Vegan diets, that would put us in a far more sustainable situation; Even just reducing meat consumption would have huge benefits. But when talking about the environment, take care to highlight that as far as helping solve climate change and our sustainability problems, Veganism is only part of the solution (albeit a very large one), and it alone will not solve the entirety of these problems, or even most of them, considering that animal agriculture accounts for about 15-20% of all global emissions. It's still easily the biggest thing the average person can actively do something about, and is an essential part of a green future, but not the end all be all. More significant changes will result in changes in infrastructure, by shifting our grids from fossil fuels to nuclear power and renewable energy.
The reason why many vegans cite animal agriculture as the main cause of climate change can be attributed to the documentary Cowspiracy, a documentary that discusses how much animal agriculture contributes to climate change. While the overall message of meat consumption being bad for the environment is correct, the paper cited by the documentary that outlines the impact of animal agriculture has severely flawed methodology, which includes a lot of "double counting" which inflates the actual figure into the 51% seen in the documentary.
Still, it's important to highlight the very much high amount of emissions from animal agriculture, and can be incredibly persuasive towards younger, progressive people. Just do not overstate its true effect, which damages the movement's credibility in the same way any bad argument would.
But it's important to keep the environmental argument as secondary to the ethical argument because not all animal products are equal in their environmental footprint. By a rather large margin, beef and dairy products account for the largest carbon footprint in animal agriculture. This isn't to say that poultry, eggs, and pork don't cause unnecessary emissions, but it's much harder to make the environmental case for them. While the ethical argument applies very strongly for all these animal products, the environmental argument mainly concerns products from cattle, which means that while people may make an effort to reduce consumption of beef and dairy, they may compensate for it by eating more poultry for example, which will hurt many more chickens. They also need to be given a reason to avoid other animal products too, which the ethical argument adequately accounts for.
Health
Health is probably even moreso vulnerable to mispresentation, when the role of diet needs to be exaggerated in order to make some arguments for Veganism in this department.
When discussing the health arguments, the main thing to talk about is generally how to be healthful on a Vegan diet, mentioning the proper sources of nutrients, particularly for calcium, protein, and iron, and highlighting the unhealthfulness of eating meat as far as is scientifically verifiable. This is where you need to be careful; A "perfect vegan diet" (even if there is such a thing) can only protect a person so much from disease. About a third of all cancers are linked to poor diet, meaning that two-thirds have nothing to do with it, and 30% of deaths related to heart disease and strokes aren't significantly linked to poor dieting. Yes, vegans, even those following a whole-food plant-based diet can still get sick and die from cancers, even heart attacks and strokes.
Do not overstate the health benefits of Veganism, ever. Similar to overstating the environmental arguments, it opens Veganism up to criticism and damages not only your credibility, but the credibility of the entire movement. If you really want to be on the safe side, just refer people to the consensus of Vegan diets by the Academy of Nutrition and Dietetics:
It is the position of the Academy of Nutrition and Dietetics that appropriately planned vegetarian, including vegan, diets are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. These diets are appropriate for all stages of the life cycle, including pregnancy, lactation, infancy, childhood, adolescence, older adulthood, and for athletes.
And of course talk about nutrients of concern, which will usually be protein (found in beans, lentils, high protein mock meats), calcium (fortified plant milks and Orange Juice, greens, and figs), and iron (also legumes, greens, sunflower seeds). These are all cheap, and when prepared right tasty meals that can assuage the concerns people may have about going on a Vegan diet.
The health argument isn't really very consistent in terms of how applicable it is, similar to the environmental argument. If you're concerned about health, eating an unhealthy meal every now and again probably won't make much of a difference, if any really. Let's say on average four meals are eaten a day (breakfast, lunch, snack, dinner), for about twenty-eight meals a week. If you're eating a varied and healthful diet for twenty-seven of those meals, focusing on greens, nuts, seeds, berries, whole grains, fruits, and legumes, is having one triple fudge brownie ice cream sundae really going to make that much of a difference? The ethical argument does away with all unnecessary consumption of animal products and would have such a person have a VEGAN triple fudge brownie ice cream sundae instead of one made from dairy (which now exists).
It's also inconsistent due to everyone being different. While everyone can be healthy on a Vegan diet barring some extreme exceptions, not everyone may have the same health benefits from eating a Vegan diet. It might help one person lower their need for statins, but for a person who follows a similar diet but does not get the same effect will abandon their diets for something with likely more animal products.
Other unintentional consequences also mirror those with the environmental one: By not bringing up the topic of ethics, people may consume less unhealthful foods that are not necessarily vegan. Again, not all meat is equal, with beef being significantly worse than poultry and fish. A person who is concerned about health but not familiar with the ethical arguments for veganism may be perfectly comfortable eating much more poultry and fish after swapping out beef.
When looking at the whole picture, pretty much the only part where the health argument is necessary is to show that Vegan diets are nutritionally adequate. Given the ethical and to certain extents the environmental argument, knowing that we don't need it negates any need to continue doing it. The fact that meat tends to be bad for us AND the environment reinforces the point even more to show the lose-lose nature of it, but probably not essential to highlight.
