Religion may be innocent after all. Although religion is often used to control people and direct them to a desired purpose it seems it may be a victim rather than the cause of violence and war. Other philosophies may be innocent as well.
The real culprit behind the century upon century of war and violence may be the very thing that initially helped people to survive against great odds. When in its infancy humanity learned to depend upon one another and form clans… or groups. Various groups developed and competed against each other for whatever resources were available. Each group became an enemy to each other.
Individual members of this or that group adopted the beliefs of that group in order to fit in. Those that attempted to resist the beliefs prevalent in that group were excised… perhaps even killed. Each member learned to cooperate and work towards the goals set for the group, goals usually set by a dominate leader or group of individuals within that group. The members often became zealous in their efforts to reach that goal.
If it became a belief that another group was out to destroy your group, whether the belief was true or not, hatred for that suspect group was initiated and fanned into a flame. War was inevitable.
Although religion and other philosophies may provide the means to control groups, it is the group that is the source of the violence. More correctly, it is the ideology of that group that is the source of the turmoil that has plagued mankind during the entirety of its existence.