As I mentioned in the last post about early Buddhist history and why it gives me a headache, one of the stories about what was either the Second Second Council or the First Third Council features a monk named Mahadeva. The academic historians don't agree on much, but one of the things they're pretty sure about is that this guy Mahadeva never existed. Or, if someone by that name did exist, he didn't do the stuff attributed to him.
One of the reasons early Buddhist history is a thorny forest of conflicting stories is that several different sectarian groups arose fairly quickly after the historical Buddha's passing, and each of these developed its own version of what happened. Further, some of them took to making up stories to make themselves look better and other groups worse, in violation of at least a couple of Precepts. Some of those stories are still in circulation in spite of the fact that their original purpose is long gone and original context long forgotten.
Mahadeva was said to have proposed points of doctrine, to which the assembled monks at whatever council it was could not agree, and this brought on the Great Schism that caused the division of Mahayana and Theravada. I don't have all the details at hand, but it seems somebody made up the Mahadeva story early in the first millennium CE -- some few centuries after the alleged council took place -- to discredit the Mahasanghika, a now-extinct sect that developed some pre-Mahayana doctrine. The stories are, basically, some old slander that paints Mahadeva and the Mahasanghika as terrible heretics. But the stories are not based on anything Mahasanghika actually taught, I don't believe.
As near as I can tell the Mahadeva stories aren't taken seriously any more except in the Nichiren school. Nichiren (1222-1282) took the Mahadeva/Mahasanghika stories very seriously. In his collected writings Nichiren called the alleged Mahadeva and his fellow-traveling Mahasanghikas out as the worst heretics ever.
Ironically, it could be argued that Mahayana, which includes Nichiren's school, more closely resembles the actual Mahasanghika sect than any other sect kicking around in the late first millennium BCE.
Whatever. There's been chatter on message boards accusing Daisaku Ikeda, spiritual leader of the lay Nichiren organization Soka Gakkai International, of saying something nice about Mahadeva, and people are bent out of shape about it. What Ikeda might have said and whether he really said it I do not know (and, frankly, don't care). But it's clear at least some people are passionate about this.