Why SGI members are deprived of the Shakubuku Kyoten [Bible of Shakubuku]

"The Daishonin's soul would never reside within a Gohonzon he inscribed but which is in the possession of those who commit the slander of turning their backs upon Fuji Taisekiji."  Soka Gakkai Shakubuku Kyoten, p. 340

Because the Shakubuku Kyoten both supports the Nichiren Shoshu and denounces the Soka Gakkai's own actions as heresies.