I came upon a most perfect example of civic disintegration today. Perfect not just because it exemplifies the brazen meanness of people with power, but also because the incident is so inconsequential, the only reason it could possibly occur is so one person can bully another. That other being me.

It takes a lot of rules for the City of Cambridge to uphold the torch of liberal tolerance. There are signs everywhere, about dogs, children, pedestrians, cyclists, and vehicles. Signs denote conventions; signs clarify rights-of-way.

As a cyclist, I appreciate my city’s ease to navigate; though I’m amused by the novel ways we arrange bike paths. My preferred designation is simple: a painted white line on the same pavement as motor vehicles. I have a clear place on the road, separated by a curb from pedestrians, since bicycles are supposed to follow vehicle rules, not pedestrian ones.

That is too simple for Cambridge, which has too many variations. On Concord Avenue the bicycle lane is raised so cyclists and pedestrians are adjacent, a curb above cars, with separate paving and markings, bikes next to the road, pedestrians nearer the trees. This may look safer on paper but in reality it is not. Pedestrians waiting for the bus cluster on the bike lane, cars don’t see us at intersections.

I am riding east on Concord Avenue, on the bike lane, when a runner crosses the road and strides onto the curb just in front of me. We look similar: middle-aged white guys. He’s wearing ear buds. He doesn’t glance in my direction. He turns onto the bike paths and continues his stride. I call out, “Passing in the bike lane.” Nothing. I repeat, louder. I slow down, so as not to run into this man. I call out in a loud voice, “Passing in the bike lane.” No response.

I try not to jump to ill conclusions. Perhaps the man is deaf. I proceed slowly off the bike path and onto the sidewalk. Now two people are moving against protocol and I’m passing on the right. I worry he’ll shift to his appropriate lane. When I am abreast but a bit in front, I say, “You are running in the bike lane,” with more care than the sentence ought to require, but I am over polite in our prickly public domain these days. I try not to sound priggish or righteous: I just want to convey convention.

“Why is it so damned important to you?” The once silent man speaks very loud. “Just go around me, you f#@k#@g moron!”

I do as he says, too shocked to even phrase a retort. I continue on to Trader Joe’s, lock my bike, put my pannier in a basket, and roll through the aisles. Once off the bike, I begin to shake. My head spins in recrimination. What did I do or say to trigger such vitriol?

Trader Joe’s is not a good environment for somber internalizing. My cashier doesn’t ask, “How you doing today?” with his usual joviality. Anyone can see I’m upset. Yet I can’t spill woes simultaneously too vile and too insignificant to a guy in a Hawaiian shirt. Why am I so upset? Am I a wuss for letting this guy get under my skin? Has the foul-mouthed runner already forgotten me, catalogued under ‘losers too easy to pick on.’

This is how we live in the United States these days. The systems and processes that outline an orderly life are ignored. Those who can, flaunt them, with such loud derision that they leave silly souls who follow rules wallowing in doubt. Car lane, bike lane, pedestrian sidewalk; meaningless designations to the guy who plugs in his head phones, tunes us out, and stands his ground wherever he chooses to be. Might is right. The loudest voice gets the attention and his way. The prerogative of the winner surrounded by mere chumps.