The SNCC officially advocated non-violence until about 1966, but somewhere along about 1964 the first steps away from that position began to occur within the organization.

It began with a decision to allow members to carry firearms for self-protection. In fact, SNCC members took much of the blunt of the violence rained upon freedom riders and voting organizers. Once violent white racists figured out they were alienating so much of the nation with their public violence against civil rights activists, they took it underground and started laying wait and laying traps to brutalize SNCC activists out of the public eye. The perception of some SNCC leaders, including Stokely Carmichael, was that non-violence was no longer effective as a political tool once it was no longer drawing violence against the activitists in the public arena for all the nation to see and be shocked and dismayed. By 1966 the organizational leadership had shifted to those, like Stokely Carmichael, who were also moving in the direction of violent resistance and the Black Power sector of the Civil Rights movement.

It would appear this internal conflict within the organization over the sanctioning of violence was never successfully resolved one way or the other. Carmichael and others left SNCC for the Black Panthers in 1967. H. Rap Brown became the head of SNCC, renamed it the Student National Coordinating Committee, and advocated violence. He himself left for the Black Panthers in 1968. By that time, SNCC was no longer much in the way of a functioning organization.

This internal conflict regarding non-violence vs. violence reflected what was happening in the larger civil rights movement. There was considerable turmoil and disarray within the movement by 1966 or 67. King was struggling to try to keep the movement together and move it back in the direction of unified non-violence at the time of his death. It is debatable that he could have succeeded, had he lived. Within the movement, it appears he was being marginalized.

It is incorrect to make a blanket assertion that the SNCC was non-violent. It would have depended on both the point in time of which one is speaking, and given the disagreement that existed within the organization beginning in about 1964, it probably also varied by campus.

What I take from all of this is that violence begats violence.   From it's beginnings SNCC was primarily a militant non-violent organization. Some of its members were probably moral pacifists (i.e. pacifism as a moral position) and some were pragmatic pacifists. I read somewhere that the SNCC were the shock troups of the non-violent civil rights movement. As they became covertly targeted out of the public eye, it is understandable how those collective experiences eventually lead some of it's members, especially the pragmatic pacifists, to abandon non-violence as a strategy.

This is not the greatest of comparisons, but I think there is some truth in it. Malcolm X appears to have started on the other end of the path from Stokely Carmichael. They met briefly in the middle. Malcolm X was assassinated before he had walked much beyond that meeting place, and I don't pretend to know how much further in the other direction he may have walked had he lived.