The source of SGI's mistaken teachings is a lack of faith

"The proponent of the Lotus school should then say, “Do you admit, then, that you do not put faith in the Lotus Sutra? Slandering means none other than this failure to have faith. For faith may be called the source of the way and the mother of blessings.” The fifty-two stages of bodhisattva practice have their basis in the first ten stages, the stages of faith. In these ten stages of faith, one begins by cultivating a mind of faith, for evil actions and earthly desires have their source in the lack of faith."

Believing that a living mentor in the seat of the Law is the prime point of the Lotus Sutra is to lack faith. Practicing interfaith in this time of Mappo is to lack faith. Believing that a Nichiren inscribed Gohonzon is valueless because it has not been sanctioned by the Soka Gakkai is to lack faith. Teaching contrary to Nichiren regarding earthly desires is to lack faith. Throwing out a character of the Daimoku is to lack faith.