Well I don't follow any "vegan" practices, so I can't really help with the motive part. I think we (internet discourse) often put "vegans" in a box that doesn't really allow for the nuances of individuals. It's not like there is a doctrine that the "vegan" follow, at least not that I'm aware of. So can you be "vegan" and care for a pet? I don't know, but I expect different people will give different answers.
Again, you're making a giant leap to torture. My point was that current scientific consensus is a vegan diet does not necessarily equal torture. So, I'm wondering why you think it does.
Nothing excludes the care of pets. It does exclude "animals for food" "as far as is possible and practical". One could definitely extend this to animals for a pet's diet, but I'd argue it's not practical for cats because we don't yet have solid evidence that says it's safe. I just don't think it's rational to flatly liken it to torture.
I think I can see it from both sides, but it seems situational to me. Breeding cats sounds bad. For government animal shelters that run out of resources, I think the adoption of an animal that would otherwise be killed is logically consistent with the generic vegan philosophy.
The most popular take among vegans (and this is coming from a vegan myself) is that breeding animals is awful, but adopting an animal from a shelter is great.
There's a lot of reasons that vegans are not fans of pet ownership, mostly because there are very minimal regulations in place regarding their treatment. I'm sure everyone knows someone who doesn't treat their pet well.
However, once an animal is born into this world, it already exists, and there's only two options. Either we can care for it, or let it die.
That's why vegans are okay with adopting pets but not with buying animals from mills. Buying animals from mills incentives the breeders to make more, taking them from shelters doesn't profit / incentivize anyone. Let's stop making more animals but take care of the ones that already exist.