Spiritual leaders, Nobel Peace Prize winners, physicians, philosophers, theologians, naturalists, environments, scientists, throughout time have told us that when we consume the meat of the bodies of other living beings all of humanity suffers…

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“One is dearest to God who has no enemies among the living beings, who is nonviolent to all creatures.” 
Bhagavad Gita, (Hindu Scriptures, oldest human sacred text c. 2500 - 3000 BC)

“All things of creation are children of the Father and thus brothers of man. ... God wants us to help animals, if they need help. Every creature in distress has the same right to be protected.” “Not to hurt our humble brethren is our first duty to them, but to stop there is not enough. We have a higher mission - to be of service to them wherever they require it.” “If you have men who will exclude any of God's creatures from the shelter of compassion and pity, you will have men who deal likewise with their fellow men.”
St. Francis of Assisi (c.1181 – 1226)

"Of all creatures, man is the most detestable. Of the entire band, he's the one who possesses malice. He is the only creature that inflicts pain for sport, knowing it to be pain. The fact that man knows right from wrong proves his intellectual superiority to the other creatures, but the fact that he can do wrong proves his moral inferiority to any creature that cannot."
Mark Twain

“Until he extends the circle of his compassion to all living things, man will not himself find peace.” “Let no one regard as light the burden of his responsibility. While so much ill-treatment of animals goes on, while the moans of thirsty animals in railway trucks sound unheard, while so much brutality prevails in our slaughterhouses ... we all bear guilt. Everything that lives has value as a living thing, as one of the manifestations of the mystery that is life.” "It is the fate of every truth to be an object of ridicule when it is first acclaimed. It was once considered foolish to suppose that black men were really human beings and ought to be treated as such. What was once foolish has now become a recognized truth. Today it is considered as exaggeration to proclaim constant respect for every form of life as being the serious demand of a rational ethic. But the time is coming when people will be amazed that the human race existed so long before it recognized that thoughtless injury to life is incompatible with real ethics. Ethics is in its unqualified form extended responsibility to everything that has life." "The thinking man must oppose all cruel customs no matter how deeply rooted in tradition and surrounded by a halo. When we have a choice, we must avoid bringing torment and injury into the life of another, even the lowliest creature; to do so is to renounce our manhood and shoulder a guilt which nothing justifies."
Rev. Dr. Albert Schweitzer (1875-1965) (German missionary, Nobel Peace Prize winner, physician, philosopher-theologian) (for more information on Rev. Dr. Albert Schweitzer see  http://www.anaflora.com/articles/saints-sages/saint-13.html  on Anaflora's website)

"Nothing will benefit human health and increase chances for survival of life on earth as much as the evolution to a vegetarian diet. It is my view that the vegetarian manner of living by its purely physical effect on the human temperament would most beneficially influence the lot of mankind.” “A human being is a part of the whole, called by us the 'Universe', a part limited in time and space. He experiences himself, his thoughts and feelings, as something separate from the rest - a kind of optical delusion of his consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection for a few persons nearest to us. Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty. Nobody is able to achieve this completely, but the striving for such achievement is in itself a part of the liberation and a foundation for inner security.”
Albert Einstein (1879 – 1955)

“I do not see any reason why animals should be slaughtered to serve as human diet when there are so many substitutes. After all, man can live without meat. It is only some carnivorous animals that have to subsist on flesh. Killing animals for sport, for pleasure, for adventures, and for hides and furs is a phenomenon which is at once disgusting and distressing. There is no justification in indulging in such acts of brutality. In our approach to life, be it pragmatic or otherwise, the ultimate truth that confronts us squarely and unmistakably is the desire for peace, security and happiness. Different forms of life in different aspects of existence make up the teeming denizens of this earth of ours. And, no matter whether they belong to the higher group as human beings or to the lower group, the animals, all beings primarily seek peace, comfort and security. Life is as dear to a mute creature as it is to a man. Just as one wants happiness and fears pain, just as one wants to live and not to die, so do other creatures.”
The Dalai Lama, speaking at the 19th World Vegetarian Congress 1967