Is the New York subway like the London Underground? By which I mean it’s a cardinal sin here to talk on the tube, and if you’re doing it you will be furiously tutted. But no one ever actually says anything about it. That’s just outright rude.

Sounds like the guy here was a coward in any case, only saying that to you when he knew he was getting off at the next stop. What a douche. “Why” wasn’t an inadequate response, it was a sensible answer — if you have a problem with something, you should be able explain why it’s bothering you.