Pretty hard to quantify politeness. And it varies not just over time, it’s also location and social milieu. I’d tend to think the slums of anywhere, anytime, were not very civil places to be.
Tact, civility, and diplomacy are active behaviors, not just the absence of rudeness. I think we see more rudeness not just because of more unrepentantly rude people , but also because of less polite people. A lot of people who would call themselves polite still tend to feel perfectly justified in rudeness if it’s framed as vindicating themselves, proving they’re right, or making sure every knows they won’t be disrespected.
So not just more acceptance for aggressive behavior, but also less acceptance of those peacemaking behaviors that require any level of self-effacement.
To keep things polite in a group some of the people need to be willing to let other people tell them what to do. Marriage, friendship, work, somebody ‘wins’ for every disagreement, or the group falls apart.
Doesn’t have to be the same people every time, but the more people who DON’T act politely and share and take turns and all that other stuff Mommy taught you, the more those that do start to feel like they’re being screwed. So people tend to get more rude and aggressive in a group like that. I’ve been in offices like that. Where managers literal cursed each other out. Not pretty.
Which I think ties into how customer service has changed*. We’re all above being anyone’s servant but we’re all busy and want more of our tedious stuff done for us by other people who also ain’t nobody’s servant.
*I don’t think service sucks now, I think overall it’s fantastic. Less personal service yeah, but so much more impersonal service (ATM’s, direct deposit, online shopping), variety, and availability.