… and here’s the final part in my admittedly long essay:
Economics
This is what’s going to make the difference in reducing meat consumption in our world
You’re not going to get much traction arguing with confirmed meat-eaters that something they’ve been doing and enjoying all their lives is unethical. Hell, we can’t get humans to wear a piece of cloth across their face to protect other humans during a pandemic, we’re definitely not going to get those folks to give a damn about animals. Ethics will work with a few, but not the masses.
You’re not even going to get traction with arguing about sustainability or protecting life or even the source of their enjoyment - sushi enthusiasts are busy eating the bluefin tuna into extinction as just one example.
I suppose you could just BAN animal based foods to reduce availability, but an underground supply and black market would spring up - look at every banned drug, substance, or thing whatosever in history.
Even in places where meat/fish were scarce they were never eliminated as food sources. India has always had plenty of meat-eaters living next to the vegetarians.
What will work is hitting people in the purse.
One reason domestic meat is so wildly popular is that hunting is an expensive and uncertain way to get food. Even in pre-money societies a lot of time, effort, and resources went into hunting in comparison for the food obtained. That’s why most of those societies ate mostly plants.
Even now, factory farmed meats dominate the market. Ethically and sustainably raised meat is arguably so much better, but it’s so damned expensive compared to factory farming that, for the poor it might as well not exist. When you’re poor, you’ll buy the cheap ground beef over the grass-fed beef that costs four times as much because that’s what makes sense for you. Faux-meats also usually cost more than cheap factory-farmed meat at this point so again, the poorest folks - and there are a lot of them - are going to buy the real meat that’s cheaper.
But if you forbid the nasty, dirty, disease-promoting factory farming practices that WILL increase the cost of meat overall. People will buy less because they can’t afford as much. Meanwhile, promote meat alternatives - not just the faux-meats (which have their place) but vegetarian eating that tastes good but doesn’t pretend to be something it’s not. Eventually, the cost of real meat will meet or exceed the cost of faux-meats. If you can get petri-meat taste acceptable and prices down to match or be lower than real meat people will start to convert to them simply because it makes economic sense for them.
At that point you won’t need to ban meat - it will slowly (or maybe not so slowly) become less and less common in humanity’s diet. People might still indulge occasionally, and you’ll have the occasional wealthy carnivore, but just as people don’t eat caviar or Wagyu beef every day, people won’t eat real meat (domestic or game) every day. As production of domestic meat becomes smaller the economy of scale will be lost and it will become a true luxury that most people won’t bother with because of the price.
You won’t have to ban meat at all in those circumstances, you’ll have less of a social backlash (those who really, really want to have meat will be able to obtain it - it will just be expensive), and new social traditions will evolve around the new dietary customs.