Cleisthenes in Athens.
Every Hebrew leader who ever existed encouraged this.
Cleisthens encouraged people to participate in government.
The leader was Pericles.
Sparta
Cleisthens
Marcus Garvey encouraged his followers to go back to Africa and "redeem" it for their people.
Massasoit was a leader of the Wampanoag people in the early 1600s who encouraged friendship with English settlers.
Your question is too unspecific to answer properly, but I would guess Socrates.
I think you are referring to excommunication, a punishment under which people could not receive communion, among other things.
As a leader during the war he was cleverly handled it. And with the U.S.A. he found a equally strong ally. He encouraged the people that Hitler, Musaloni and the Japs could very certainly be beaten.
Malcom X was probably the most prominent black leader of the time, who preached hatred and encouraged black people to distance themselves from whites.
Your question is too unspecific to answer properly, but I would guess Socrates.