The following quotes are from The Extended Circle by Jon Wynne-Tyson, who in turn quoted them from the Congress booklet:

Jayantilal N. Mankar :
It should be realised that vegetarianism is based on the sanctity of all life. It is not merely a question of filling one's stomach with this food or that. It is a question of humane instinct and humanising man to justify his more evolved position. Merely becoming a vegetarian, therefore, cannot achieve its basic objectives unless associated with love for life through animal welfare. It is the love-prompted compassion and not merely love for a vegetarian diet which can alleviate the soul and develop the true image of Man.
- The Vegetarian Way, 19th World Vegetarian Congress, 1967

Dr. Gordon Latto :
Apart from the value of the frugivorous diet to man himself, it also brings great benefit to our younger brothers, the sub-human creatures. When we lose our sense of pity and compassion for the creatures, we harden our hearts to them and also to our brother man.
The Vegetarian Way, 19th World Vegetarian Congress, 1967

His Holiness the Dalai Lama of Tibet :
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 Vegetarian Way, 19th World Vegetarian Congress 1967

U Nu (Thakin Nu), 1907-
World peace, or any other kind of peace, depends greatly on the attitude of the mind. Vegetarianism can bring about the right mental attitude for peace. In this world of lusts and hatreds, greed and anger, force and violence, vegetarianism holds forth a way of life, which if practised universally, can lead to a better, juster and more peaceful community of nations.
- The Vegetarian Way, 19th World Vegetarian Congress 1967