Nichiren’s Tendai contemporaries … held the Lotus Sutra to be all inclusive, but generally took this to mean that, properly understood, any practice, such as chanting Amida Buddha’s name or invoking the Bodhisattva Kannon, could be considered practice of the Lotus Sutra. Nichiren decried this interpretation as a confusion of the true and the provisional and rejected all other, “pre-Lotus Sutra” teachings as no longer suited to the present time of mappō. Like medicine that stands too long on the shelf and becomes poisonous, these other teachings and the practices based upon them were, in his view, not only soteriologically useless but positively harmful. For Nichiren, to willfully set aside or ignore the Lotus in favor of other, “lesser” teachings amounted to “slander of the Dharma” and would pull the practitioner down into the lower realms of rebirth.

He therefore taught his followers that one should not only embrace faith in the Lotus Sutra oneself, but spread that faith to others, assertively rebuking adherence to other, provisional teachings. This is known as shakubuku, the “harsh method” of propagating the Dharma by actively challenging “wrong views.” Nichiren saw shakubuku as compassionate action that would enable others to form a connection with the Lotus Sutra and save them from both misfortune in this world and rebirth in the evil realms.
A Buddhist Kaleidoscope; Jacqueline I. Stone, When Disobedience Is Filial and Resistance is Loyal: The Lotus Sutra and Social Obligations in the Medieval Nichiren Tradition, Page 264

For Nichiren, the inherence of the pure land in the present world was not merely a matter of philosophical or contemplative insight; when individuals realized enlightenment, he taught, their world would be materially transformed:

When all people throughout the land enter the one Buddha vehicle and the Wonderful Dharma [of the Lotus] alone flourishes, because the people all chant Namu Myōhō Renge-kyō as one, the wind will not thrash the branches nor the rain fall hard enough to break clods. The age will become like the reigns of [the Chinese sage kings] Yao and Shun. In the present life, inauspicious calamities will be banished, and people will obtain the art of longevity. When the principle becomes manifest that both persons and dharmas “neither age nor die,” then each of you, behold! There can be no doubt of the sutra’s promise of “peace and security in the present world.”

This passage points to both continuities and breaks between Nichiren’s teaching and broader, contemporaneous currents of Buddhist thought. Teachings about the nonduality of this world and the Buddha’s pure land, expressed in such terminology as “the sahā world is the land of ever-tranquil light (shaba soku jakkōdo)” or “worldly truth embodies ultimate reality (zokutai nishin),” formed a standard doctrinal feature of both Tendai and Shingon esoteric Buddhist traditions. Similarly, belief in the apotropaic powers of the Buddha-Dharma to ensure harmony with nature and prosperity in the social sphere also was a common assumption underlying the sponsorship of esoteric rites for nation protection (chingo kokka). Nichiren’s distinctive reading of these ideas derived from his “single-practice” stance: The ideal Buddha-land could be realized in this world, but only by exclusive faith in the Lotus Sutra.
A Buddhist Kaleidoscope; Jacqueline I. Stone, When Disobedience Is Filial and Resistance is Loyal: The Lotus Sutra and Social Obligations in the Medieval Nichiren Tradition, Page 263