Have you ever experienced fundamentalism in Buddhism?
Personally, I have barley encountered fundamentalism from an overall school, but I have from members of both Nichiren and Tibetan. Then again, I only experienced it from a few members of very large schools; so I'm not sure if it would be fair to classify the schools themselves as "fundamentalist".
Nichiren Buddhism is very arguably fundamentalist, but not necessarily in a negative sense. It is Lotus Sutra fundamentalist, to be more precise.
Nichiren was Tendai, but he wanted Japanese Buddhism to be uniform, and admit only the Lotus Sutra as scripture. In this kind of exclusive insistence on the Lotus Sutra, he diverged from Tendai teaching, and so his following eventually became a movement all it's own after his death.
Nichiren Buddhism is one of the so-called
Kamakura schools, because during Japan's Kamakura period- Japanese Buddhism enjoyed something of a thought revolution. Several new schools came about, including Dogen's Zen.