Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
The objective of any Dawah work should be to give a good service to Islam and Muslims. So, if a group commits itself to make Dawah (call for Islam) its members are required to make consultations among themselves and advise one another as to reach an appropriate conclusion.
The rules concerning the leader depend on whether he is a group leader or a nation leader. Obedience to a group leader is not compulsory while obedience of state leaders is compulsory as long as they do not order followers to do something against the Sharia. As for the group leader, his prerogatives are defined by the group members themselves.
So, if the group members after consultation give him the right to have the final word regardless of what the majority says then his decision is binding on all of them. But, if they say that the opinion of the majority is binding on everybody, then he should comply with that opinion.
So, this matter depends on the agreement that the group members decided beforehand. But the final and ultimate goal should be to work for the benefit of Islam and Muslims.
Allah knows best.