@davidrevoy Depending on culture, various behaviors are highly politicized (or not). So things that may be neutral or at best friendly courtesy for you can be (to cut it short a bit) a tribal sign elsewhere, and if you're (not) doing certain things, you're mistaken to be part of the "enemy tribe".

While I agree that this seems childish (I'm probably closer to your culture than to @Elfie@bae.st's), maturity seems to be an insufficient perspective: we probably have similar signals that look obvious and important for us while others just roll their eyes at our sensibilities and are shocked or even appalled by our strong reactions.