I'm first and foremost promoting discussion of a topic that is relevant to many people in the veg*n community. I feel that encouraging discussion of relevant topics is one of my duties to the forum. I haven't made up my mind on the issue, but I try to read up on the various links that have been posted here, and whatever else I can find.
The idea is that through informed discussion we can arrive at some kind of conclusion based on knowledge, evidence, deduction, logic, science. Emotions probably won't contribute much that is useful.
I'm copying a pasting what I posted in the other thread you started on the same subject:
Obligate Carnivores' Nutritional Requirements
Cats are obligate carnivores and are very different from dogs-and people-in their nutritional needs. What does it mean to be an obligate carnivore? It means that cats are strict carnivores that rely on nutrients in animal tissue to meet their specific nutritional requirements. In their natural habitat, cats are hunters that consume prey high in protein with moderate amounts of fat and minimal amounts of carbohydrates. Cats also require more than a dozen nutrients, including vitamins, minerals, fatty acids, and amino acids. These nutrients are the building blocks of various structural body tissues; are essential for chemical reactions (metabolism, catabolism); transport substances into, around, and out of the body; supply energy for growth and maintenance; and provide palatability.
The important thing to remember about nutrients, particularly vitamins and minerals, is that your cat needs the correct amount-but no more. It is possible to have "too much of a good thing" when it comes to vitamins and minerals; the use of supplements not only is unnecessary but also can be potentially dangerous to your pet's health. A key point to remember is that cats are neither small dogs nor people. Because of cats' unique metabolism, what might be good for you might be detrimental to your cat. A high-quality cat food assures an adequate supply of vitamins and minerals in your cat's diet; supplements should never be added without a veterinarian's approval.
Another important nutrient with respect to overall health is water. Water helps regulate body temperature, digest food, eliminate waste, lubricate tissue, and allow salt and other electrolytes to pass through the body. You should provide your cat with clean, fresh water at all times.
http://www.vet.cornell.edu/fhc/health_resources/brochure_feedingcat.cfm
A few sites to get you started on learning about the importance of minimizing carbohydrates to maintain urinary tract health and minimize the risks of death from urinary tract blockage, kidney disease, chronic UTI's, etc:
http://caturinary.com/articles/Cat_Urinary_Tract-Food.htm
http://www.catinfo.org/?link=urinarytracthealth
http://www.allthebestpetcare.com/urinary-problems-in-cats/
This link is a starting point to valuable information about the effects of grain in cat food and carbohydrates specifically in the development of feline diabetes (just follow the links from the site):
http://www.yourdiabeticcat.com/
And remember, these discussions aren't even about a vegan diet, they're about diets which contain grains and other carbohydrates. When you start basing an obligate carnivore's entire diet on food that are harmful to him even in smaller measures, you are exponentially increasing the health risks. Also, urinary tract issues and diabetes aren't the only health issues associated with feeding grains and other carbs to obligate carnivores, but it should give you a start on educating yourself.
One thread on this subject might be considered to be an attempt to inform yourself about a subject about which you yourself (in the other thread) admitted you know nothing. A second thread, in such short order, looks like an attempt to drive up traffic on your site at the expense of the health of cats. Yes, I tend to be emotional about people who further their own interests at the expense of the health of other animals, especially if such people profess themselves to be ethical vegans.
I've read that if you feed a cat a vegan diet, you also have to give them a taurine supplement as it only occurs naturally in meat, and without it, cats can go blind. I have no idea what, if any, other kinds of supplements would be needed.
The primary danger of a lack of/insufficient taurine is heart health. Cats who lack sufficient taurine in their diets die of heart failure and other heart related issues at a relatively young age. Cats get taurine from eating the hearts and other organ meat of prey. Commercial cat food is also supplemented with taurine, because it breaks down during cooking/processing.
), cats are at high risk of developing lower urinary tract disease (FLUTD), diabetes, and organ failure as a result of poor diet. A few years back, my cat Milo was eating a crummy brand of commercial cat food and ended up with a urinary blockage. After being treated in the hospital with a urinary catheter followed by two weeks of antibiotics, changing his diet to a different brand was all it took to keep potentially fatal blockages from reoccurring. It just goes to show how important a role proper diet plays in both treating acute problems and managing chronic illnesses in cats. That's the main reason why I would not mess with my cat's diet. 
