In today's society staring is considered rude because it makes some people feel uncomfortable. If you stare it makes people feel like something is wrong, or makes them think you are creepy.
The guy is probably making her uncomfortable, staring at her like that. Staring is rude.
Staring is rude when anyone does it, so please try your best not to stare.
Staring wide-eyed and rude and stupidly.
Glancing is perfectly OK Staring (that is over 10secs, or 5secsx 5) is RUDE Tell him how you feel about it.
He was staring at her, lost in her beauty. The entire room was staring daggers at the new arrival.
what's the considered rude or polite of Greenland
After all these years of him not noticing me, finally, he was staring straight at me: and I liked what I saw.
It's considered rude everywhere, not just Germany.
its not considered a swear, but it is considered disrespectful and rude,
It is considered rude not to try to speak a little Spanish (even though many Spaniards - especially in tourist areas - speak English). It is also considered rude for American tourists to wear shorts along with loud colored (e.g. Hawaiian style) shirts. It is considered rude to speak loudly in close quarters. It is considered rude not to provide a tip to those in the travel, entertainment and hotel industries. And there are many, many more examples.
Politeness is a cultural construct. Some societies have decided that one of their rules is that staring is impolite. This is probably an outcome of the embarrassment factor from being stared at. In some strata of society it is held that to be looked at is some kind of threat and they will therefore react with aggression, rather than mere disdain. For instance, think about it this way. If you are standing in front of a bunch of people, and all of them suddenly start staring at you and you don't know why, you WOULD be embarrassed, wouldn't you?