How about this: Politeness is objective, and the opinions about how politeness is carried out is relative to culture. Just a proposition. There's a distinction between politeness opinions and objective politeness.
But its weird - when I'm impolite, I know it, and the other person knows it. No way can I rationalize a way to say "we have different opinions" Every time I'm impolite, I know it and they do too. I feel like I'm breaking a clear rule when I'm impolite.
Check solitary walker's post for further info, but I'll give my own take (again) here XD
Politeness in and of itself isn't objective. 'Being rude' is often heavily cultural, as in the ONLY reason yeu 'know' yeu're being rude, is yeu intentionally act so against yeur own cultural upbringing.
There can be some really really screwed up forms of 'rudeness' which is why there's even such a term as 'culture shock'.
For example, in holland, it's considered excessively rude as a guest, to not eat every last thing placed before yeu on a table given to yeu by a host. This was quickly discovered by the people housing a pair of boarding students when they kept eating everything, and the adults just figured they were really hungry, and the kids were begging them silently to stop giving them food because they were full long ago, but had no choice as it'd been ground into their mentality to such degree. There was no 'please no more' allowed culturally as even that would be considered highly offensive.
It's hard NOT to offend another culture due to things like this, it's entirely cultural to the point that yeu could not possibly hope to even guess whot their ideals are, or whot they consider 'polite'.
For an even stronger example, we can go back to the original introduction of modern manners.
Louis XIV wanted total, absolute, pure power. He subverted the other nobles through bizzare cunning, by adding such things as fashion and manners, which changed literally weekly, so that they would invest all their time learning new manners, all their finances in buying new clothes to match the trends, and at the same time, he would offer noble titles to anyone who was willing to pay for them, meaning that the power distribution was greatly widened in general by the fact that there were so many MORE new nobles to spread it between, but focused on himself because all these NEW nobles were pouring all their money straight into Louis himself, meaning HE had monies, all the other nobles were broke, either from paying for the title, or from spending all their time and money on the rapid pace of fashion and manners.
At one point, due to this weaponized version of manners, it was customary for everyone to trim all their fingernails quite trim, EXCEPT for the nail on their left pinky finger. If yeu wanted into a room, it was considered impolite to knock on the door, that would be highly rude and offensive. Instead, yeu had to scratch on a the door with yeur left pinky, in which case a servant specifically paid to do nothing except sit at the door and listen carefully, would hear yeu and let yeu in.
And thus even the "knock before entering" rule we have now would've been considered highly offensive, as it could interrupt a discussion at a table. Whot's good manners to us, would've been highly offensive to another culture.
So no, there isn't really an 'objective baseline' of manners, because even the most basic of concepts can be highly subverted by culture.
A recent past one for the states, and still sometimes considered so today in select areas... a white person waving at a black, though INTENDED to be friendly, was highly offensive to the whites in the area, and sewed great fear into the black population for the eventual retribution they'd face.
A more modern one would be excessively retarded feminists, who if yeu hold the door open to them, will be PISSED OFF that yeu basically implied they were too weak to do it themselves. (even if yeu hold the door open for everyone behind yeu just to be kind, regardless of gender)
Quite bluntly stated, there is no standard, other than personal and cultural. One man's politeness, is another's insult.