Nichiren is [sometimes] portrayed as an aggressive and even violent fanatic. The extravagant vows that he makes are sometimes cited as evidence of this. For instance, Nichiren vows to never give up the Lotus Sūtra even if someone offered to make him ruler of Japan or threatened to kill his parents. Is this unreasoning aggressive fanaticism, however? Or is it simply a refusal to cave in to bribes or threats? I would note that Nichiren’s parents had already passed away when he wrote this, so this was a bit of rhetoric on Nichiren’s part. What is often overlooked is Nichiren’s caveat: “… I will not submit to them until a man of wisdom defeats me by reason.” Was this empty rhetoric? Why even put that caveat in there? In fact, the whole of the Kaimoku-shō up to the point where Nichiren expresses this vow is a marshaling of texts to support Nichiren’s case that the Lotus Sūtra is the ultimate teaching of the Buddha that should not be neglected, derided, or subordinated to lesser teachings. Now we may or may not accept Nichiren’s reasoning, and may or may not find his proof-texts and the presumption of scriptural authority they rested upon convincing, but I do think Nichiren put in quite a lot of effort to present a well-reasoned case and that as far as he was concerned no one had provided him with any adequate response to the case he was making for the Lotus Sūtra (and against its detractors). Instead, he had been physically attacked on several occasions, banished twice, and almost been executed.
Who exactly was being unreasonable and fanatical about their beliefs? Nichiren, who wrote long essays citing the Buddha’s teachings in order to clarify the Buddha’s true intention? Or those who were trying to silence and even kill him? And what was Nichiren advocating as the ultimate teaching based on the Lotus Sūtra? I rather like the way it is put in Reply to Hoshina Goro Taro (Hoshina Goro Taro-dono Gohenji), a letter attributed to Nichiren.
In Buddhism that teaching is judged supreme that enables all people, whether good or evil, to become Buddhas. Surely anyone can grasp so reasonable a standard. By means of this principle we can compare the various sütras and ascertain which is superior.
(Gosho Translation Committee 1999, p. 156)