Is there any greater arrogance than SGI having no scriptural proof for their doctrines of interfaith and mentor in the seat of the Law?

"In the more than 2,220 years since the Buddha’s passing, neither the Buddha of the “Life Span” chapter nor the five characters that are its essence have been propagated. When I consider my present rewards, I wonder whether they do not perhaps exceed even those of Dengyō and T’ien-t’ai, and surpass even those of Nāgārjuna and Vasubandhu. If I had no scriptural or doctrinal proof for this, how could there possibly be any greater arrogance?"