Unfortunately, cats are obligate carnivores, so they MUST have meat in their diet. No ifs, ands, or buts about it. I would expect someone who is concerned enough about animal welfare to go vegan would be aware of the fact that an animal described as an "obligate carnivore" has its own dietary needs that, in spite of thousands of years of domestication, have not changed.
If you are concerned about the source of the meat in your cat's food, stop feeding commercial food, find a source for organic meat, and make your own food.
And please read the following websites, that explain in further detail WHY cats cannot exist on no-meat diets.
http://catinfo.org/
http://feline-nutrition.org
http://healthypets.mercola.com - this site has an extensive article library, so you'll have to do a search for the proper articles.
http://www.littlebigcat.com/nutrition/vegetarian-cats/
If you are concerned about the source of the meat in your cat's food, stop feeding commercial food, find a source for organic meat, and make your own food.
And please read the following websites, that explain in further detail WHY cats cannot exist on no-meat diets.
http://catinfo.org/
http://feline-nutrition.org
http://healthypets.mercola.com - this site has an extensive article library, so you'll have to do a search for the proper articles.
http://www.littlebigcat.com/nutrition/vegetarian-cats/