NYC may in fact be polite, from their perspective.
In NYC, there's always too much going on. The critical thing people lack is time. So they interact in ways that don't waste time. That may be being polite... in context.
Yep. If you're a tourist standing, blocking the subway door like an idiot and not paying attention, you can expect a loud "get the FUCK out of the way!" from a New Yorker and probably a shove. It's definitely going to feel shockingly rude, but the reality is that you're preventing a dozen or so people from getting on or off during the limited time the train is stopped, interfering with people who just want to get to work or get home. Ie, you're the one being rude and selfish and the New Yorker is just correcting you as quickly and effectively as they can.
In NYC, there's always too much going on. The critical thing people lack is time. So they interact in ways that don't waste time. That may be being polite... in context.