NYC is comprised of 10,000 different neighborhoods. You may not know the names, but you know the faces. Last week I was in my local deli and came up short a few bucks and the guy said, “pay me tomorrow.” That kind of thing happens all the time.
In regards to multiculturalism. It exists for the simple fact that people are in a confined space and have to get along to do business. And then there are distinct neighborhoods with distinct cultural flavors.
What most people take as rude is actually a form of honest efficiency.
However, the two main points that not many outside of NYC realize are these:
A)NYers live a great deal of their lives in public. The home is usually not the center for entertaining or being entertained. Even folks with large apartments entertain outside their home since friends are scattered throughout the city and it’s convenient to meet in a central location.
B)NY is about commerce. It’s the most capitalistic city on the planet. All of the liberal stuff is strictly for show.
Non New Yorkers will very often mistake the speed and urgency at which New Yorkers conduct themselves to that of being "rude".