Pets that are obligate carnivores/omnivores...

[brimstoneSalad]

Obligate carnivores should not be our pets (cats are not obligate carnivores, there is plant-based cat food with the nutrients they need).

As far as I understand it, cats are obligate carnivores because their liver cannot produce the amino-acid called taurine.

Whether a carnivore is obligate or not is a question of ecology, and doesn't speak to human environments.
A dog could be vegan in "the wild" without the benefit of human technology. B-12 from coprophagy etc.

Taurine is found only in animal products and a little in wheat. It's not at all trivial to make cat food that's entirely plant-based and contains enough taurine.

It is trivial, with supplementation. However most vegan cat food seems of be of questionable quality, and only some cats take to it well. Cats are more difficult than dogs in many ways.

I also think that cats should not be kept as pets because they don't actually love their owners and would probably kill and eat their owners if given a chance to.

That's pretty speculative.
There are plenty of people who even keep large cats like lions and tigers who do not kill and eat their keepers when given the change. Some do, of course, others abstain and choose to play, purr, etc. Unless you're asserting that domesticated house cats are actually less capable of human bonding than lions and tigers (which would be an absurd argument given the normal effects of domestication), it's undeniable that there are plenty of domestic cats who would not kill and eat their owners. I would have no problem believing that many WOULD do so, but making such a general statement puts upon you a burden of proof you could not possibly uphold and which goes against all available evidence.