In Texas, the school board was populated by young earth creationists. Because of the size of the market, they could dictate that textbooks be rewritten, such as adding creationism along side evolution in science classrooms [1]. Religiously-motivated thinking is behind many important laws and denying things like climate change [2]
And in some countries, a particular religious belief is all-controlling and holds political and judicial power as well. Non-believers, homosexuals, and apostates get killed. Women are possessions.
I know the grandparent comment is getting down-voted because it is very broad. It is easy to reflexively downvote the edgy atheist. Of course Christianity (or choose another religion) has good aspects to it. But it isn't just atheists scoffing at what they feel are absurd beliefs: Christians of one flavor laugh at the absurd beliefs of other flavors, believing their own group is the one that got everything right. Biblical literalists get laughed at by other Christians for thinking the world is 6000 years old. Non-Catholics laugh at Catholics for thinking a consecrated Eucharist is not just a symbol of the body of Christ but becomes the actual body of Christ [3]. Mormons consider themselves Christians but many Christians do not think they are. And so on.
[1] https://www.npr.org/2012/06/20/155440679/revisionaries-tells...
Interesting fact that I learned recently. Christianity is the reason we don't marry our cousins, and it is believed that the genetic benefits increased human intelligence by a considerable margin.
Hmmm... maybe, loosely, in the way that it's the reason we don't murder people either, but there are plenty of non-Christian societies with incest taboo. I would guess most.
The fact that we celebrate Christmas in 202X by buying crap on Amazon instead of torturing the infidels suggests that we do indeed get tired before we get dangerous, at least on the long arc of history.
[1]: https://www.youtube.com/watch?v=gRdfX7ut8gw