There are some who strongly believe in the Lotus Sūtra, but they do not denounce the enemies of the sūtra. Even if they do good deeds, read and copy the Lotus Sūtra ten million times, and master the heart of the “3,000 existences contained in one thought” doctrine theoretically, if they do not denounce the enemies of the Lotus Sūtra, they cannot attain enlightenment.

If a man who has served his emperor for ten or twenty years knows an enemy of the emperor but neither reports him to the emperor nor drives him away, it will negate the credit of his longtime service, and he would instead be punished. You should know that people of today thus commit the sin of slandering the Lotus Sūtra.

Nanjō Hyōe Shichirō-dono Gosho, A Letter to Lord Nanjō Hyōe Shichirō, Writings of Nichiren Shōnin, Doctrine 3, Pages 141.