Nichiren taught with Sutra in hand

"When ordinary people in this latter age read these various sutras, they suppose that these sutras accord with the mind of the Buddha. But if we ponder the matter closely, we will see that in fact what they are reading is only a reflection of their own minds. And since their own minds are naturally uncultivated, there is little merit to be gained thereby." - Nichiren

Their teachings accord with the minds of ordinary beings in order to sell their "product" to ordinary beings. We teach with sutra in hand in accord with the mind of the Buddha. That is why Nichiren's teachings are so difficult to believe and understand.

On the other hand, Nichiren (and we) teach in accord with the mind of the Buddha:

"The Lotus Sutra, on the other hand, is known as a sutra that was preached in accordance with the Buddha’s own mind. Because the Buddha’s mind is an excellent mind, persons who read this sutra, even though they may not understand its meaning, will gain inestimable benefit.

Mugwort that grows in the midst of hemp, or a snake inside a tube [will as a matter of course become straight], and those who associate with people of good character will consequently become upright in heart, deed, and word. The Lotus Sutra exerts a similar influence. The Buddha will look upon one who simply puts faith in this sutra as a good person." - The Bodies and Minds of Ordinary Beings

Our teachings are the most difficult teachings to believe and the most difficult to understand. The established sects will not teach authentic Nichiren, because being difficult to believe and difficult to understand, few people will accept them and they will lose their revenue streams. 

In Nichiren's most important  writing we read:

"With full understanding of Shakyamuni’s teachings, the four great voice-hearers said, “This cluster of unsurpassed jewels has come to us unsought.” They represent the world of the voice-hearer that is within ourselves. The Buddha stated, “At the start I took a vow, hoping to make all persons equal to me, without any distinction between us, and what I long ago hoped for has now been fulfilled. I have converted all living beings and caused them all to enter the Buddha way.” Shakyamuni Buddha, who has attained perfect enlightenment, is our own flesh and blood. His practices and the resulting virtues are our bones and marrow. The “Treasure Tower” chapter of the Lotus Sutra says, “He who is capable of guarding the Law of this sutra will thereby have offered alms to me and to Many Treasures.... One who guards this sutra will also have offered alms to the emanation Buddhas who have come here adorning and making brilliant all the various worlds.” Shakyamuni, Many Treasures, and the Buddhas of the ten directions represent the world of Buddhahood within ourselves. By searching them out within us, we can receive the benefits of all these Buddhas. This is what is meant by the following passage: “If one listens to them [the preachers of the Law] for even a moment, one will immediately attain supreme perfect enlightenment.” The “Life Span” chapter reads, “It has been immeasurable, boundless hundreds, thousands, ten thousands, millions of nayutas of kalpas since I in fact attained Buddhahood.” The Shakyamuni Buddha within our lives is the eternal Buddha since time without beginning, who obtained the three bodies more than numberless major world system dust particle kalpas ago. The “Life Span” chapter states, “Originally I practiced the bodhisattva way, and the life span that I acquired then has yet to come to an end but will last twice the number of years that have already passed.” He was speaking of the world of the bodhisattva within ourselves. The bodhisattvas, as numerous as the dust particles of a thousand worlds, who emerged from beneath the earth, are the followers of the Shakyamuni Buddha present in our lives. They follow the Buddha just as T’ai-kung Wang and Tan, the Duke of Chou, served as ministers to King Wu of the Chou dynasty and later assisted his son and successor, the infant King Ch’eng; or just as the Chief Minister Takenouchi supported Empress Jingū and later her grandson Crown Prince Nintoku as a highly valued minister. The bodhisattvas Superior Practices, Boundless Practices, Pure Practices, and Firmly Established Practices represent the world of the bodhisattvawithin ourselves. The Great Teacher Miao-lo says: “You should understand that one’s life and its environment at a single moment encompass the three thousand realms. Therefore, when one attains the Buddha way, one puts oneself in accord with this fundamental principle, and one’s body and mind at a single moment pervade the entire realm of phenomena.”

Mark Rogow disciple of Shakyamuni Buddha and Nichiren Daishonin