It´s true that the men here act more aggressively than in N. America, but what that guy did is completely out of line in any culture!!! I hope there is no next time, but if there is, don´t be afraid to make a scene -- with so many pairs of eyes around, people will take notice and will help you out.
I´m speaking from personal experience -- once when I was just walking down the street (one I´ve walked dozens of times, just in Caballito in broad daylight), this guy on a red motorcycle just started following me, circling around me on the sidewalk and saying really inappropriate things... he even touched me, it was really frightening! The street was empty, but the moment I screamed, several people ran out to see what was going on. They were very sympathetic and asked their neighbors further down the street if they saw anything, etc. even offering to call the police.
Anyway most of the time when subtes and colectivos are super-crowded, to me it always seems that people are hyper-aware of personal space here and try not to touch, at least not without a ¨pardon¨ or ¨disculpa¨... that is, after that one person squeezes into the door at the very last second!