You never know what’s going to put someone over the edge. The straw that broke the camel’s back probably looked like any other straw.

For Charlotte, it was walking out of her house a month ago and stepping in soft dog shit on the way to her car. For me, it was Charlotte’s response to stepping in soft dog shit on the way to her car.

To be thorough, we’d both been going through a rough patch. I now know that Charlotte had recently lost her life partner to another woman, and I’d lost a raft of clients, which happens cyclically if you serve small businesses but which invariably brings me down.

All I knew (at first) was the surreal scene in her parkway, unfolding on my left as I walked home from the grocery store one Sunday. It was an eyespanking cheekslapping afternoon. Copenhagen blue sky pocked with puffy clouds. I was striding along with my two shopping bags, when suddenly: “NO DOGS!” screamed a cardboard sign on foot-high sticks, planted in the weedy grass between the sidewalk and the street. And “NO DOGS!!” blared another, shorter, four feet further. I turned in my tracks so swiftly the shopping bags knocked into my thighs. I read the biggest sign, aimed the way I’d been walking. It was about 18 inches off the ground and after “NO DOGS!!!” it said “CLEAN UP AFTER YOUR ANIMAL!”

This seemed to be an hysterically strong response to an invisible threat. My first wonder was whether the resident went off his or her meds. This is Berkeley after all. Then I tried imagining what could drive anyone to plant such signs.

The yard was unexceptional. Offensively low-maintenance: juniper and camellias near the one-story gray stucco edifice, ratty lawn elsewhere, all shaded by a big parkway elm. Only ginger rock and ivy would have been worse. I wondered what the resident was trying to protect.

I began walking again and I started to get angry. I’m like most dog owners: responsible. I don’t let Pippi out without me. I use a leash unless there’s clearly no one around. I carry a bag for scooping her poop. I’ll admit that, very occasionally, when my supply of plastic bags and patience is low and my social resentment is high, when no one appears to be looking, I walk away from Pippi’s shit. I feel a little young and reckless doing it, like when I dare to litter the floor of the bus. But mostly I’m socially ept.

So I was surprised about my anger at those signs. But I flashed on a high school memory. Some movie in Driver Ed called “Courtesy is Contagious.” It showed a woman driver pleasantly waving another driver into traffic ahead of her, and that other driver then behaving well to the next person he encountered, and so on, extending to people holding doors open for those behind them and all the way to smiling at passing strangers. I remember thinking it was hokey but completely true, and 40 years of life experience haven’t contradicted it.

But at the same time that I “got it” about courtesy, I also understood the contagion of rudeness: a person offended is a person ill-disposed toward others, tending not to inhibit his own offensive behavior.

I took a lot of offense at those signs. I felt my heart swell with determination to somehow say fuckyou right back at the sign-planter. And nothing arose in me to inhibit that determination.