nailed it

"I'm a recreational walker, and in the last few years I've noticed something odd when I've hit the sidewalks of suburban St. Louis and suburban Colorado: a not negligible percentage of the men speeding by me in their cars or sport-utility vehicles (it's always men) feel moved to yell obscenities at me.  It's hard to know why they do this...My guess is that they yell at me simply because I'm a stranger, and from the perspective of their glassed-in vehicles I have no more human reality than the coach on their TV screens who has elected to punt on fourth and short."

"Jane Jacobs identified as a hallmark of city life the existence of privacy in heavy crowds -- a privacy whose maintenance depends not on the pseudoparental expedients of isolated houses and controlled shopping environments but on modes of adult behavior best learned in public places like the sidewalk.  That the country's widely decried 'breakdown of civility' began at home, rather than in so-called urban jungles, can be confirmed at any movie theater, where audiences accustomed to watching videos in the bedroom have forgotten how to shut up."

from "First City" in Jonathan Franzen's How to Be Alone