While both dogs and cats belong to the class carnivora, this doesn't mean a lot, so does the panda bear which is near vegan. By nature cats and dogs wouldn't eat anything like what is commonly found in a can of pet food either. Vegetarian cats should be fed it as a supplement. Taurine deficiency can result in blindness and even death.
Cats also require pre-formed vitamin A and arachidonic acid.
All known vegan cat foods contain these essential ingredients and the companies listed below provide them in their cat foods. Ask your vet about changing your pet's diet if concerned. Also animals don't have morals or beliefs. They do whatever is necessary to survive, with no preference one way or the other about the impact on anything else. The same applies to using killed insects for broaches, crushed insect wings for irridescent eye shadow, or dying insects in jumping beans.