I guess it balls down to individual definitions. I never agreed to that since religion in and of itself isn't like choosing what we want to take for class in college. I'd assume if we take up a religion whether we decide it's right or go by what other things is right, it should define our lives.
Actually experience and fact. It's similar to Catholicism and Protestantism. At first, Nichiren Shoshu Buddhism in Japan dictated who was to be enlightened and how. Then politics got involved and Soka Gokai International (SGI) disagreed. The priesthood excommunicated many members because of it.
There are a lot of bias opinions from both sides. This one is from the
Nichiren Shoshu view. I went to this temple for a couple of years. When I first went, they shoved magazines saying SGI was false and how Nichiren Shonin is the real Buddha of today. (Reincarnation of the original Buddha). You can't be enlightened without the priesthood. You also can't chant at any other meetings such as SGI and Nichiren Shu among others only Shoshu.
Even though they all chant the same thing, Daimoku, like Catholicism, without the "Sacraments" of the temple and priesthood, the mixture of the two is a no-no. A lot of people in the 80s I think got their Gohonzon from the priesthood taken from them because the follower decided to leave the temple. Nichiren Shonin did not say which Gohonzon was right. He even told followers to create their own. So there is a huge political upheaval between the two.
Here is information on
Sokai Gokkai International. They also gave me pamphlets against Nichireh Shoshu with their magazine. They have a sensei that most people look up to even across the states. It's a form of idolism because all of our meetings is based on his interpretation of Nichiren's letters and Sutras not our own interpretations as The Buddha taught.
In short, the former Nichiren Shoshu because of the politics, if one is part of SGI or Shu, one can't be follow Shoshu Buddhism. In America it's a bit more relaxed but I can't imagine in Japan and other countries. SGI looks down upon members who are Shoshu adherents. When I told them I was a former Shoshu follower, they gave me pitiful looks as if Shoshu was, well, I can't think of a good phrase, evil. The groups I practice with are friendly just the president/sensei focus bothers me.
Here are some more links.
Leaving SGI to return to Shoshu
(ShoShu) Clarification on attending SGI Activities
I would have been more devoted in the faith if not for the politics involved. As for who can be involved and who can't, it balls down to politics unfortunately. Nichiren Shoshu believers tend to lend towards getting you not to go to SGI. It's highly evangelical. SGI is more sensei oriented and chanting for things rather than what The Buddha actually taught. So, there are some loop holes and that's why people are influence outside or inside the faith because of it.