They are a cult started by this white man:
They provided a vital counter-message about Black awakening during the Civil Rights movement and generally provided an outlet and means to join several other key groups in attaining a better standing in society. During this time, Malcolm X became essentially the face of the NOI. After a while, Malcolm became very hesitant to some of Elijah Muhammad's actions, including censoring him and preventing him from working with other key figures at the time. The final straw came when Malcolm learned Eljah was going around sticking his dikk in the young NOI female staff (while married). The famous picture of Malcolm holding a rifle was actually his fear of the FOI, as they had ordered essentially a hit on him. You don't have to believe me, hear it from Malcolm himself about fearing for his life due to NOI threats:
Then we have various footage of Malcolm's family saying that the NOI/FOI killed him. You also have a speech from Farrakhan essentially bragging about killing him:
The videos don't lie.