Hey gurm,
Great to know you liked the responses.
I do not live with other animals, so I'm not the best to answer this. I know about lots of people that live with Vegan dogs who strive on their diets. I think the matter is a little harder with cats (although there are healthy vegan cats too). There is a lot of info about it on the net.
I know some older members here live with vegan dogs. Jeff and Desert Girl live with two, and I think that Kathy also lives (or lived?) with vegan dogs. They could help you more specifically (if they are still coming to the forum).
Do we have a right to decide what "our pets" eat? Well, we do that on a daily basis, don't we? I seriously doubt that most "pet owners" ask the dog or cat "what would you like to eat today?"
I guess the first question should be, do we have a right to own other animals (as pets, or as milk/egg machines, subjects of experimentation, etc.)?
That's another question that, if you're interested, we could debate later.
But since there are lots of domesticated animals today, and we ought to take care of them now, I think that those that say to people who choose to make their non-human partners "how can you impose your views on them? You don't have the right to do so" forget too easily that almost everything we do with them could be described as an imposition on our part: the decision to buy/adopt/rescue, say, a dog (nobody asks the dog if she wants to go here or there, with this family or that); the food we give them; at which hour and for how long we "take them out"; or when we take them to the vet, etc., are all decisions WE make (impose on them?), and they play no role on the decision.
So I don't know what's the difference between these choices, and the choice to feed a dog a vegan diet.
I'm pretty sure that most dogs don't want to go to the vet, let alone get a shot. But we do it anyway, because we care about their health. Well, when we choose to make the dogs that live with us go vegan, we do it because we care about them, but also because we care about all the other animals exploited by humans for their selfish reasons. It's just an expansion of our circle of moral consideration.
Those are my points of view. I'll let others give you the specifics.
Kind regards,
Samuel.