It doesn't make sense wtf????
Of course it makes sense, there's several things to consider though.
Sometimes you may hear this from people who generalize once they encounter some tourist (or citizen) from that ethnicity/group, leaving aside the ones who don't, so they'll just focus on the bad. To give an example, I once saw a chinese guy talking on the phone by screaming & talking nonstop, the entire street was flooded with this guy's voice, I assure you someone in there must have though "why are the chinese so loud", not only because of the stereotype that they are, but because people generalize for much less.
Yet, I've also heard that the chinese can be very quiet, so here you have someone who under certain circumstances, will go towards what their bias says.
Second, the ones you hear this from may be accustomed to a place where they are quieter, and in comparison, the others will be louder. Like if you take some nordic guy and put him in a bad neighbourhood in Italy, Spain or Mexico. They will for sure notice the difference when they encounter some retard in the street screaming/calling for their friends, 2 meters away.
Third, notice how you're mentioning inferior cultures when it comes to politeness (for common people) with those who surround you. More than half of your examples are essentially third-worlders in regards to this, yes there are very polite people from those cultures, but in general, they're not.
That's why you never hear "the japanese are so loud", because generally their culture puts politeness as a higher priority than in other places (even if neutral, meaning, they will
try to not bother you).
