My issue with vegan cookbooks

I've began researching Veganism for a project that I will be starting soon. Recently, I've been going through a number of vegan cookbooks and it seems they're is one consistent factor that plagues them. Moral superiority. Moral superiority in regards to health and environment. The first two chapters always go into great detail into why vegans are better than anyone else. From what I've seen, which I could be wrong about, human beings throughout mankind have been omnivores. Proof lies in the teeth. Our canine's are proof of our natural drive to eat meat. Although I'm not sure whether Veganism is the healthiest option, or if it's the most environmentally responsible way humans can get they're food, but until we know more Vegans shouldn't speak in absolutes.