I find most of "politeness" is playing a game where you're not supposed to say certain things and not supposed to talk about certain things, and the end result is that it seems it was deliberately designed to be crippling. Folk spend so much time worrying about how to wink-wink nudge-nudge a topic that they end up never discussing it at all. "He misunderstood!" Yeah it would be a lot easier not to "misunderstand" if you said it straight out.
The undiscussed topics end up piling up until you have no genuine relationship at all.
The first dynamic seems to be overreacting to over-sharers. Hey, uh, you're not supposed to talk about how you have to clear your sinuses with saline regularly the second time you have a conversation with someone. Folk experience this and develop an allergy, meaning they won't talk about it ever. At some point in the relationship you are, in fact, supposed to share these things. Admittedly I don't know when exactly. Much like Plato never saw an aristocratic society, I see a lot of over-sharers and a lot of never-sharers, so I'm not terribly familiar with what a healthy golden mean looks like. Merely: due to the fundamental theorem of algebra, it must exist.
At some point the relationship is supposed to stop being polite. At some point trust is supposed to be earned.
At some point even if trust isn't earned, you're deeply involved enough that impolite topics become relevant.
Part of the reason you should reject Americoid socialization is because they have a severe narcissism problem. Narcissists functionally have no boundaries, so they treat everyone the same. They can't tell the difference, after all. Either they're impolite to everyone, or they're polite to everyone. Either they'll tell you about their anal hernias after knowing you for five minutes, or they'll treat you like a retail cashier even after knowing you for ten years. You get them a hard chair as present, and they'll pretend to like it - while you're looking. Either way it's a big WTF moment.
Because narcissism is so prevalent in hyper-Christian America, even non-narcissists end up behaving this way, because they think you're "supposed" to. Like me, they never see anyone but over-sharers and never-sharers.
In part this is the middle class foolishly trying to ape upper-class behaviour, and confusing viper-pit court politics with upper-class behaviour. Trust no-one, because everyone is plotting to overthrow you or use you as a cat's paw to overthrow someone else. Mai heero, yeah? Egalitarianism means we're all lords, which means we're all supposed to be backstabbing traitors, right?
Seems like most can only make friends in childhood, because you're not socialized yet. Automatically don't over-share because children are shy, and automatically share enough later because they're bad at keeping secrets and generally don't know how you're "supposed" to cripple all your relationships.
Americoid socializing is so bad it only works if you're socially incompetent.
Hard times are hard. On one prong you have to suffer the fake and gay relationships you get. Either you drive away the "polite" folk who are disgusted by over-sharers and are limited to the low-end crass folk, or you eliminate the possibility of genuine intimacy, nipping it in the bud. On the other prong, you have to re-derive culture from scratch, or go looking for very specific foreigners to imitate on very specific points.
P.S. Alcohol as "social lubricant" apparently means you can use "I'm drunk" as an excuse to be impolite without being labelled an impolite person and shunned by "polite" society.
This means going out to drink isn't for having "fun" it's about deliberately risking having a fight, because you can't have a real discussion about anything unless you're drunk. Naturally since you can't bring up the topic immediately, the frustration and resentment builds up and it's a much worse fight than it inherently has to be.
Yeah it's super fun to have a fake relationship except when you're "drunk" wow why didn't I think of this awesome state of affairs.
P.P.S. On one prong you're "allowed" to say rude things. Being impolite doesn't necessarily mean being tactless, but having rejected any sort of filter you can't ask someone to use tact either. Being rude is practically required. Feels weird if you're all being total shitheads except this one guy, you know? Stands out in a bad way.
On the other prong, you're allowed to be passive-aggressive. You can say the most insulting things as long as they're phrased "politely," because it's "impolite" to point out the insult.