Here's my vegan take on it, for what it's worth:
Humans created the issue of domesticated animals. Thousands of them are put to death every year simply because humans won't own up to this responsibility. I don't think that's fair. We created this situation, we have to take on the responsibility. Taking on that responsibility requires us to do two things:
1 - DO NOT INCREASE DEMAND. This means avoiding breeders and companies that use animals at all costs. There is absolutely zero justification for continuing to breed animals for human pleasure, consumption, entertainment, or science experiments. Do not purchase pets from breeders, don't go to the circus, don't use products that test on animals, avoid unnecessary medical procedures, and be an advocate and activist when and where you can - speak for the animals and try to get horrible practices (like circuses and vivisection, to name a couple) outlawed.
2 - TAKE CARE OF THE ONES THAT ARE HERE. This means adopting/rescuing if you have the financial means, time, and energy to care for an animal. I see nothing wrong with rescuing or adopting an animal brought into this world because of the selfishness of humans and giving that animal the best life possible. In fact we owe it to these creatures, in my mind.
So... Yeah. That's my view, in a nutshell. It can be a complicated issue because certain domesticated animals are obligate carnivores - like snakes and cats. If that is too tricky an ethical issue for people (and I see how it can be), there are plenty of dogs, rodents, etc. who could use good homes and can thrive on veg*n diets.