Two facts that get under Soka Gakkai members' craw

I). The Ongi Kuden is "pius" or not so pius forgery probably created by a Fuji School (Nichiren Shoshu) priest:

1).The Ongi Kuden is not in Nikko’s hand nor is it ever mentioned (“again”) by him. There is no authentic seal of Nichiren (colophon) except for a later legendary accretion referencing a serpent who was to have appeared to Nichiren and Nikko as he was lecturing on the Devedatta Chapter. 2). It is supposed to be based on the Chu Hokkekyo, the authentic Annotated Lotus Sutra of Nichiren, the original copy exists on Mt. Minobu. The problem is it doesn’t conform well to it. Only 23 passages of the 133 passages from the Chu Hokekyo appear in the Ongi Kuden. 

3). No mention of the Ongi Kuden or the Ongi Kikagaki occurs before Nitcho’s Keiun Sho in 1503. These were competing texts used by opposing sides in the Nichiren ichi-shoretsu debates (the harmony of the 28 chapters of the Lotus Sutra versus the superiority of the essential teachings debate), held at this time. “Dueling Oral Teachings” 

4). The Ongi Kuden mirrors the writings of the Tendai sect. They employ the Tendai sect formulations of Kanjin style interpretations of “progression” and “resemblance and reversal” to represent concepts found commonly in Chuko Tendai (original enlightenment) doctrine. These conflict with the authenticated writings of Nichiren, most notably, the Kanjin Honzon Sho, as seen above. 

5). The text contains comments regarding events that did not exist at the time of the supposed lectures: 

A). For example the Ongi Kuden refers to the “six senior disciples” but Nichiren did not designate these six senior disciples until a few days before his death, some years later B). According to scholars and priests of the orthodox sects, it refers to Nichiren as the “eminent founder,” a term which did not come into usage until well after Nichiren and Nikko died. C). The text of the Ongi Kuden also refers to a document which was written some 13 years after Nichiren’s death, the “K’o-chu” which is a Yuan-dynasty commentary on the Lotus Sutra by Hsu Hsing-shan dated Yuan-chen 1 (1295). D). Finally the date it was supposedly approved by Nichiren (who then supposedly affixed his seal), is the first month of the first year of Koan but the era changed its name from Kenji to Koan on the 29th day of the second month. There was no first month of Koan. E). Additionally during the time the lectures supposedly took place and Nikko was supposedly transcribing them, he was not at Minobu where the lectures were held. He was in the Fuji area on a shakabuku campaign. 

6). John Petry wrote: “The Nichiren Shoshu has pointed to a reference in another writing in a text by a Fuji school priest in the 1600′s referencing the existence of a transcript of lectures given by Nichiren in his life time but there is nothing in that reference to indicate what document he is referring to or even whether it was simply a copy of the Ongi Kuden or the Onko Kikigaki which were known to exist at right around 1500.” 

7). Nichiren disparaged oral teachings. Since the core Taisekaji doctrines can not be found in the authentic Gosho, the Oral Teachings as well as many forged Gosho were invented by them.

Some examples that Nichiren eschewed oral teachings:

"Answer: Are those who have received the teachings directly from their teacher invariably free from error, while those who appear in later ages and examine and clarify these teachings are to be regarded as worthless? If so, then should we throw away the sutras and instead rely upon the four ranks of bodhisattvas? Should a person throw away the deed of transfer received from his father and mother and instead depend upon oral transmissions? Are the written commentaries of the Great Teacher Dengyō so much trash, and the oral traditions handed down from the Great Teacher Jikaku the only guide to truth?" - The Doctrine of Attaining Buddhahood in One’s Present Form

"In like manner, though Jikaku may have studied under the Great Teacher Dengyō and received instruction from him, and though Chishō may have obtained the oral transmission from the Reverend Gishin, if they go against the teachings recorded in the authentic writings of Dengyō and Gishin, then how can they help but incur suspicion?" - On Repaying Debts of Gratitude one of Nichiren's Five Major Writings

The Ongi Kuden (Record of the Orally Transmitted Teachings) goes against Nichiren's authentic (authenticated) writings, for example, The True Object of Worship for Observing the Mind and the Opening of the Eyes.

II). Daisaku Ikeda changed Nichiren's Four Dictums.

Nichiren's Four Dictums:

“But I, Nichiren, one man alone, declare that the recitation of the name of Amida Buddha is an action that leads to rebirth in the hell of incessant suffering, that the Zen school is the invention of the heavenly devil, that the True Word school is an evil doctrine that will destroy the country, and that the Precepts school and the observers of the precepts are traitors to the nation.” - Letter to Dōryū of Kenchō-ji

Daisaku Ikeda changes Nichiren's Four Dictums:

"To merely repeat the four dictums simply because they came from the Daishonin, while ignoring people’s feelings and the changing times, is to overlook the Daishonin’s spirit. The four dictums are then nothing but dogma. That is what gives rise to the devilish aspects of religion. It is people and the heart that count. The four dictums are the manifestation of the Daishonin’s firm conviction to resolutely battle the devilish functions that serve to confuse people." -- Daisaku Ikeda