The best argument - I say this as a meat eater who routinely considers a vegan diet, and has experimented with it in the past - isn't ever related to things like intestinal length, teeth, or other hallmarks of what "our ancestors" supposedly ate. The army of keto dieters, along with the army of herbivores suggests that we are capable, biologically, of being omnivores. No amount of propaganda from either side ever convinced me of anything which was contradicted by my first-hand experience.

The best single argument is simply this: we can choose to go on a hunger strike. We can choose to diet. We can choose low-salt foods when we crave salt, for a variety of health reasons.

We are rational animals, and the rationality we have is as much a part of us as the instincts of a cat to kill a bird is.

And perhaps in the past we did not know we had a choice of what to eat. Perhaps life was brutal and we were coarsened to the suffering predation caused, because we lived under the Law of the Jungle.

But now we live in civilization.

Philosophy, religion, science, and media, however, have given us tools to look further and deeper into existence; to examine our own consciences, and so on.

And we do not need meat to survive, even if we can digest it fine. We can live healthy, longer, and arguably (taking into account what subreddit I'm in) more ethical lives without consuming animal flesh, and all of the suffering, pollution, and resource depletion that causes. We can make that rational choice, and the cost is, we give up some of the sensory pleasure of eating animal products.

When a vegan comes up to me and says that -- that's an argument I can't argue against.

Only people particularly predisposed to propaganda (and there is a lot of out there, both pro and anti-meat) are likely to join the "humans were never supposed to eat meat, biologically speaking" brigade. I've watched vegans try this for decades with meat eaters, and while I'm sure it succeeds with some people, it's the weakest tool in the vegan's arsenal.

The Big Gun? All of those animal cruelty videos you all hate to watch. They are the Big Gun because they impact people viscerally (and when they make some stupid comment about how all that carnage "looks delicious" or how they're "craving bacon," that generally means they're feeling uncomfortable.) And all it takes to opt out of this brutality is to say, "No, I'm going to have some produce today instead." It is a choice, like our politics are a choice, or our jobs or anything else is a choice.

The tragedy of what vegans face is that they are taken to task, mocked, and attacked, for what is - even in the most brutal carnivore's analysis - a surfeit of empathy and compassion. Like the worse you can say is, "Vegans are wrong, but wrong for the right reasons."

I am still not sure animals have rights, in the context I've studied "rights" for many decades.

I am positive, though, that I hate to see anyone, or any thing suffer. And sometimes, rarely, late at night in the dark house here, I step on one of my cat's tails, and I feel like shit about it for a good hour.

And that cannot compare to what happens in a slaughterhouse.

Closing the "abstract" vs "real and in front of me" gap is the real challenge and difficulty for vegans, and these Ag-Gag bills indicate that meat producers know it.

So the next time you run into an argument like you mention - canine teeth or whatever (frankly the degree to which the smell of cooking beef makes me salivate - I know this disgusts a lot of you, but not me - is all the indication I need to know that I can eat and enjoy meat, provided I don't think about how it got to my plate) - just say, "I choose to eat vegetables because I despise suffering, and there's too much of it in the world, and I don't want to be a part of that."

Because when you make it about you (notice the "I choose..." language), the person listening can't really circle the wagons as if he's being attacked -- though he'll want to if he feels guilty -- and at the same time you're framing it as a personal choice.

Ideally you want the most petty people you encounter to not want to have to live with the fact that you're working harder to live a more ethical life than they are. That cognitive dissonance, when you can lob it into someone's head (and you can never do that by beating on people -- that just raises psychological self-defenses) that what they claim to represent, and how they actually live, are at odds with each other, is how you make more vegans.

That, and, some good meals, as well. People do not understand that vegans make some delightful foods from a pure taste perspective.

Meat eaters think of veganism and they think of one thing and one thing only: salad. Subsisting on it. And only it. Forever.