Challenge, maybe not, but noone even asked what he was doing- it's NYC, how many of those people probably have camera phones they could've taken a picture with and called police? And yet, at most, people just casually look at him, or in Hector's case, help...

EDIT: Not to mention these are crowds of people, in broad daylight... I doubt anyone with a bit of sanity would attack someone in broad daylight, with that many witnesses (and most likely security cameras)