Listening to SGI leaders, you would think that fundamental darkness is all that Nichiren talked about. They go on and on about your fundamental darkness [it's always your fundamental darkness, never their's]. Nichiren mentioned "fundamental darkness" ten times, "fundamental delusions" twice, "possessed by devils" once; and "fighting evil" never once in ~ 1500 pages of writings.
Shakubuku, on the other hand is mentioned, deconstructed, and analyzed by Nichiren at length hundreds of times in many dozens of writings. "Break and subdue" is one translation of shakubuku, another is "forceful practices", and still another, "to refute." Nichiren rarely performed the forceful practices on his own believers. Compare this to SGI leaders who, drunk on power and ego, are always performing the forceful practices on their members.