No religion has neither been a force for good, or a force for bad.
Humans are tribal. We evolved to protect people we feel connected to, and to fear, distrust and fight people we don't consider to be similar to ourselves. This is not only true of every human since their first were humans, it is also true of other social primates from Gorillas to Chimpanzees.
This is a function of human nature.
Of course the world view and social identity of any culture plays into this. And religion is a big part of this.
Then there is the problem of defining what "religious means". Are the nominally atheistic cultures that feature a supreme "beloved" leader a form "religious". What about cultures that are based on the idea that "all men were created equal". Isn't this a religious foundation?
Even if you could define religious. And, even if you only consider theistic religions I don't think there is any evidence that "non-religious" societies have been any less tribal, or violent or brutal.