The Vegan Diet is one which is completely free from consumption of animal products. We choose this diet because it is a non-violent diet, one that does not participate in the violence of killing animals.
In looking at human animals and what might be a natural diet, one must consider that animal husbandry has been utilized only for a small portion of human existance. Prior to that time, eggs were probably occasionally consumed, collected from the wild, but it is very unlikely that humans consumed any non-human milk products. Consumption of milk from another species is an extremely unnatural activity. Consumption of milk beyond infancy is not practiced by any other mammal on the planet. It likely that the animal portion of a natural diet would consist of small amounts of meat, insects and eggs.
Some people feel that consumption of meat, eggs and/or dairy are required for humans to be healthy. This is simply not the case. There are many examples of extremely healthy people who eat a vegan diet. The only known nutrient which is challenging to obtain on a vegan diet is B12. This micronutrient is however available in several vegan foods such as spirulina, nutritional yeast, tempeh, miso and other bacteria rich cultured foods. Eating fresh picked greens, one is also likely to eat a few aphids and other even smaller creatures, which will also contribute towards one's B12 intake.
While it may be true that conditions on farms do not have to be so oppressive as they currently are, while it is true that less violent farms can be created, even organic and free range farms, while using less intensive methods, still rely on mass processing and handling of the animals because of the large numbers of animals involved. All of these farms still do as much killing of animals (as a percentage) as do commercial farms. If they do not do the killing themselves, they sell their unwanted and "worn out" animals to others who kill them. If you want to remove your support for the meat industry and its violence, it is impossible to do this while eating dairy and eggs unless you can find a personal supplier who provides retirement for its older animals (good luck).
I have a friend who raised free range organic chickens to sell the eggs. The chickens had lots of space to run around and were well cared for. When broods were hatched to continue to provide more chickens, male chicks were immediately killed after they hatched. When the hens past their peak breading age, they were slaughtered and their meat sold as free range chicken. Eventually my friend tired of the work and decided to change occupations. She killed the rest of her chickens and sold them as meat.
My personal opinion is that any ownership of animals ultimately creates a dynamic where the animal is percieved as a commodity as an egg, milk or meat producing unit. This perception allows the owner to kill without remorse and deadens their compassion towards other living beings, including other humans.