It's hard to tell a cat what to eat or what not to eat. I posted about that in the thread. We had cats at home when I was a kid, we fed them regular (non vegan) cat food, but they also constantly killed mice and bugs and stuff like that. Apparently domestic cats decimate bird populations, and they kill way more than they actually eat.
All of that is irrelevant though. That thread is full of people who saw the words "obligate carnivore" and immediately inferred that a cat that doesn't eat meat will die. That's logically and scientifically ridiculous and ignores the actual definition of an obligate carnivore. So the stupidity was unbearable. It's fine to get into a careful dicussion about cat nutrition involving veterinarian advice and scientific studies and reach a pro or anti vegan conclusion. But saying "obligate carnivore" as a thought-stopper and having it work on the site admin just showed that the site was too messed up to engage with. Simliar debates happen on Wikipedia all the time but each side brings miles of citations to the table. I.e., they would have at least weighed actual facts instead of stopping after a slogan decided everything.
Fwiw someone in the thread said that cats require taurine (an amino acid) in their diets and that taurine isn't found in plant sources, but that it can be synthesized. Does a plant diet with synthetic taurine supplements give a healthy cat all by itself? IDK, but it means that the topic is more complicated than "obligate carnivore, hur hur!!".
No that's wrong, https://en.wikipedia.org/wiki/Carnivore#Obligate_carnivores , "Obligate or "true" carnivores are those whose diet in the wild requires nutrients found only in animal flesh." The key words are "in the wild". As I mentioned in my post that I linked, it's quite difficult (though possible) for humans to live purely on wild plants. Vegan humans usually consume a lot of beans and grains that have to be cooked before eating, i.e. transformed to a state not found in the wild. But then they do fine. Is the same possible with cats, particularly if can you add synthetic amino acids? Maybe yes, maybe no, but it's a biology question that isn't disposed of by the words "obligate carnivore".
Preferences aren't that relevant. Humans by nature usually prefer beer and doughnuts over anything healthy. They have to consciously override that impulse or end up like Homer Simpson.
Also regarding evolution, cats aren't just carnivores, they're predators. Their natural diet is meat that was killed just moments ago. If feed them instead on canned meat that was killed months ago, you're turning them into scavengers, not so natural. Cows and chickens, of course, didn't evolve to live in factory farms either.
Again though whether vegan diets are good or bad for cats is completely irrelevant to the stupidity of that thread. Even if you think it came to the right answer about cat diets, a stopped clock is right twice a day. The issue is rejecting any type of careful thought or research in reaching the conclusion, not the conclusion itself.
No I don't have a cat. We had cats when I was a kid and we fed them cat food with meat in it (the concept of vegan cat food would have been totally alien to us at that time). We didn't underfeed them. The cats killed mice and bugs anyway. They do that, it's called "overkill", a biology term that describes a predator animal killing more prey than it needs to eat. As I mentioned too, the cats even tried to feed US sometimes. They occasionally brought home dead mice or birds that they dropped in front of us. I don't think we ever ate any though.