As a guy who sells vegan cat and dog food, here's the perspective that I take on the issue:
It is an individual choice, and I neither condemn those that continue to feed meat to their cats and dogs, nor do I believe it is the "only way" that some people tend to think because it's an absurd, outdated notion that still clings to life through ignorance. There have been THOUSANDS of healthy, happy vegan cats and dogs out there over the past few decades, so anyone who wants to say that it isn't healthy is misinformed. If a quality food is used (NEVER try to make your own vegan food from scratch, particualrly for cats, unless your plan is to kill them slowly!) that contains all the essential nutrients and amino acids, then you have no worries going with a vegan food.
Unless you're turning your cat or dog loose to hunt their own food, you're giving them something unnatural, so let's not kid ourselves that a fancy $4 can of free-range meat based dog or cat food is the same thing they'd eat in the wild. When you're giving your dog a bowl of renderings and fillers that's formed into kibble or a meaty sludge, that's not any more natural of a diet than one based on vegan foods. That's just the way things are - I get a LOT of people who write us to antagonize the vegan perspective for foods, but come on, since when does a dog go out and naturally eat venison? Or kill a cow for beef? When does a cat catch a fish or eat a duck in nature? When you open a can of cat food and find nothing but a whole dead squirrel inside, then you'll finally have your "natural" option, but let's not kid ourselves that we're keeping close to nature when we feed our companion animals. Dogs aren't completely carnivorous, they're scavengers and are very good at existing well on whatever they come across that seems like it's good to eat. Ever been to a country like Jamaica where wild dogs just roam around freely? They're not going home to have someone feed them at night - they pick through trash, eat carcasses, leftover vegetables discarded by vendors, or whatever else they find when they're hungry. Cats don't NEED MEAT, they NEED TAURINE and ARACHADONIC ACID, which is normally in meat but can be created synthetically, as is used in the products we carry. If you can keep an open mind to that and get past the B.S. that gets perpetuated so often, you can start to see how a vegan diet for animals is not necessarily any less healthy or any more dangerous than standard rendering-based foods.
Cats and dogs are like people, though - some will absolutely thrive on a vegan diet (we've had quite a few people tell us how their animal's health improved considerably after the changeover), and we've had people say that their animals didn't take well and they went back to a meat-based diet. Every creature is its own entity, and much like how some people go vegan and feel great, others have a more difficult time because they haven't figured out how to balance things adequately for proper nutrition. Choosing to have a cat or dog go vegan isn't something to take lightly, and should only be done with research and plenty of consideration, not to mention having your veterinarian follow the animal's health to ensure that things are going well. It is something that needs to be done responsibly, as the health of the animal comes first and foremost - anything done without that in consideration is cruelty, particuarly anyone who forces a diet on an animal that just can't seem to adapt to it in a healthy manner.
What people also need to consider is that feeding a cat or dog a vegan diet isn't all-or-nothing. You CAN give a cat or dog a 25%, 50% or 75% vegan diet and still make a difference. Even a 50% reduction allows some people to feel that their animal can have balanced nutrition and still work to reduce suffering through decreasing their purchase of animal by-product based foods. It's much like with people - if you found NO way to feel good on a completely vegan diet (hypothetically speaking, of course) but found that eating vegan for 80% of your diet worked perfectly, why would you not consider being 80% vegan? It's not a black-and-white issue - every little bit helps when vegan food is put in place of meat-based animal foods, even if it's just a little bit mixed in with the gross stuff.
I can rant about this stuff all day, but I'll end it here. Remember, it wasn't that long ago that people in general thought that a vegan diet for humans was ludicrous and would lead to a quick death. Why do so many think that animals are so different and can't go vegan as well?
Yes, Yes and Yes... I find your dissertation a pleasure to read as well as very informative. Your pointing out the ambiguity of the subject definetly makes your argument a very credible one... you may have even swayed my opinion a little bit, Good job