Religion is only a thing because it was created by people who didn't know where the sun went at night. Therefore, as our species progresses and becomes more intelligent it's only natural that we'll move away from stories that were created to explain the unexplainable. As for the effect of less religion on society, I would offer that my kids (currently 10 and 11) are being raised without religion in our household and, by any measure, they're most well behaved and well adjusted kids I've ever seen. It's not religion or faith that leads to a good and successful life...
But we are answering a lot more questions vis-a-vis the natural world and it's working that was explained away as "gods will"
Dsispas posted a good podcast from NPR about a theory on the origins of religion (worth a listen if interested). Basic premise was as the tribes grew larger than it was incapable to recognize people as good/bad then the stories began to define the good communal and are lessons for morals. J. Peterson also has a interesting theory based on the hierarchy of natural selection to define a warrior/leader figure in which the stories are premised and then handed down.
It's been speculated that we've already hit the tipping point and are gearing up to begin the regression (of the masses anyway) now. https://www.sciencealert.com/iq-sco...y-intelligence-boom-flynn-effect-intelligence
I'm confident any wiping out of tribes was most masterfully accomplished by white christian invaders from Europe.
The thing is, you and they live in a society created by Christianity. You can't escape its influence on your social mores. The history of Christianity is the history of Western Civilization.
The book of Matthew is the answer that you are probably looking for, but the fact is that the same concept is a part of just about every religious dogma that exists.
Personally, I'd say it's not a problem. Not having a religion doesn't make you're a troublemaker, morals and values don't come from religion.
You need to go read the history as a lot of tribes in the west were wiped out by other natives. Hell, the anasazi basically wiped out themselves. But for the most, their immunity to infectious diseases took the most heavy toll on the native population. Disease reduced the native population by 2/3 by 1790's which is before the westward expansion.