Starting to suspect that some weaker form of "without religion everyone would act like monsters" is in fact true, in a way that's not convenient for anybody. Even in a world where humans were, like, psychologically incapable of believing in the paranormal, there are plenty of obvious prosocial, reasonable, even self-serving if you simply must frame it that way, reasons to not go around killing and robbing and raping everyone. But I do think that "without some prestige-having order one incurs social costs for rebelling against, the behavior of a large-enough-to-change-things number of individuals will default to socially-corrosive levels of selfishness, cynicism, and paranoia" is a much more defensible construction. It's only recently that we have the technology to potentially destroy everything beyond repair, at the low ebb of such a cycle.
Here's a poll from Gallup, another from the WSJ, both showing sharp declines in the self-reported importance of values/life goals like patriotism, religion, having kids, hard work, and community involvement (the last one they differ on admittedly; Gallup shows an increase, WSJ a decline) over the last 25-30 years, both showing increases in the importance of money. (tbc, I think a large part of the decline is justifiable--those 'institutions' fucked up in important and damaging ways during that time frame. But my point is they happened, they color how people see the world.) And I don't know if people have just never seen those polls or don't believe them, or what, but I suspect it's because it doesn't make anyone look good. If you're a liberal/progressive who thinks nationalism and religion are mind-viruses that hold society back, you should be troubled that sharp declines in their social value have seemingly not improved the world. If you're a libertarian who thinks rational profit-seeking can solve our social ills, it should bother you that people care about money more than ever at the exact moment the social order seems to be breaking down. If you're a communist who thinks that cold, hard material analysis is the only thing that matters, that the other stuff is bullshit exploiters use to keep class consciousness from developing, well, congrats, everyone's a materialist now, the opiates of the masses aren't getting anyone high anymore, but I can't imagine you're pleased with the state of things either.
It's been remarked upon many many times how shockingly nihilistic Trump and co are when you really break down their rhetoric: the flag-and-cross stuff is for the rubes, all he cares about is getting rich, punishing slights, and owning the libs. They say whatever comes to mind and don't care if it contradicts the rest because who reads anymore? This is in some ways better than someone genuinely, earnestly trying to reset the clock to 1954, worse in others, but I do think they're different. Because whatever you can say about American-golden-age conservatism, "a sharp decline in the importance of patriotism, religion, and family" is certainly not among them. That style of conservatism is flailing as much as anything is. Trumpiness is a cross-ideological phenomenon: the qualities that allow it flourish in such an environment also define the backlash to it. Everything you don't personally approve of is a conspiracy against you, everything is someone else's fault, no one you can't personally vouch for can be trusted, good-faith communication and taking ideas seriously are for suckers.