It never ceases to amaze that there are people who are vegetarian because they feel or at least in part because they feel animals are treated poorly in our modern food chain. The closer one looks the more frequently it is uncovered that these people are cat owners. Not cat owners on the big ranch who let the critters loose on the natural fauna of the farm, but cat lovers in suburbia or the urban core who are responsible and keep their pets indoors and take great care of them.
Here's the rub. Cats are obligate carnivores. This means they must eat meat protein. Dogs can get away with more grain or carbohydrates in their diets but Cats don't get anything from them. And the ultimate irony that whether one feeds human grade food or pet food the animal protein comes from the very same supply chain, the very same slaughter houses, the very same farms.