For much of history, religious tolerance has been the rule and religious intolerance the exception. Before the rise of monotheistic semitic religions in the last 2000 years, violence for religious reasons was largely unknown. People of the ancient age (the age before the last 2000 years) fought for all kinds of reasons but hardly ever in the name of their God.
The monotheistic God is a jealous God, an exclusivist God, and an intolerant God. He is not the God for everyone, only for his chosen ones. He promises to deliver his flock of chosen ones to heaven and utterly destroy the unbelievers who refuse to worship only him. He seeks to create a world in which his chosen ones rule, and only he is worshipped. In the last 2000 years, the armies led by this God have swept the world to conquer and convert.
The polytheistic God is syncretic, inclusive, and broadminded. He resides in everyone and everything. Anything—a rock, a tree, a figurine—can be the symbol of this God. Due to his syncretic and inclusive nature, the polytheistic God does not divide the world between the chosen ones and the unbelievers. He does not lead armies to conquer and convert because of the polytheistic belief that God is in everyone and everything.
In the last 2000 years, the polytheistic God has faced a significant political disadvantage. The monotheistic cultures developed political unity under the banner of “One God.” With this unity they created powerful armies. The polytheistic societies remained without political unity, and they could not develop powerful armies. In most parts of the world, in the clashes between polytheistic societies and warlike monotheists, the former lost.
Mankind cannot live without God, so atheism is not an option. The choice is between the polytheistic God and the monotheistic God. Religious harmony is not possible until there is a return to polytheism—I don’t think such a return is possible, since the monotheistic movements are very powerful.