Nichiren Daishonin in his writings states: “The heart of the Buddha’s lifetime of teachings is the Lotus Sutra, and the heart of the practice of the Lotus Sutra is found in the ‘Never Disparaging’ chapter. What does Bodhisattva Never Disparaging’s profound respect for people signify? The purpose of the appearance in this world of Shakyamuni Buddha, the lord of teachings, lies in his behavior as a human being” (The Writings of Nichiren Daishonin, vol. 1, pp. 851–52).
By this the Daishonin means that the heart of the Lotus Sutra, the highest among all of Shakyamuni’s teachings, resides in the practice carried out by Bodhisattva Never Disparaging of respecting and paying reverence to all people. The life of each and every person is endowed with the buddha nature, the seed or potential for attaining buddhahood. So long as a person pursues the correct path, this seed will invariably sprout, blossom, and bear fruit. It was on the basis of this firm conviction that Bodhisattva Never Disparaging paid obeisance to every single person that he encountered.
To encourage and bring to fulfillment this practice of paying respect to others, we may say, constitutes the Buddha’s basic aim, the true message of the Lotus Sutra, and the true propagation of the Lotus Sutra. In order to achieve the ideals and spirit of the Lotus Sutra, Nichiren Daishonin made this most important practice the very core of his being. Moreover, he revealed Nam-myoho-renge-kyo of the Three Great Secret Laws1 as the manifestation of his own life embodying the buddha nature, and for the sake of all people of the future, opened up the path that would lead to inner transformation, or human revolution, and the creation of a peaceful and ideal society.
---> http://www.nichirenlibrary.org/en/lsoc/Foreword/1#para-6