If the shaman has *any* veto power, then it's still arguments from authority. At the end of the day, the shaman's opinion is still undebatable.
If the shaman has no say in the matter, and it's not based on a "the majority is right" fallacy, then it's not a religion: it's an assembly of people discussing their belief , voting for no apparent reason, and then leaving each having their own belief. A majority vote *can't* force someone to change his beliefs *unless* he believes the majority is always right.