I stood frozen in a parking lot one day as a middle-aged woman screamed at a child she was extracting from a car seat.

She used expletives. She called names.

What to do? My stomach churned. This did not seem like an offense that warranted a call to authorities. And yet, I wondered if the woman knew how scary she sounded, and if the preschooler was subjected to more than verbal abuse at home.

"Can I help you?" I finally managed to squeak, cautiously approaching their car. The woman scurried away, ignoring me, pulling the child along.

That awkward moment came to mind recently as I listened to debate prompted by the arrest of NFL player Adrian Peterson after he allegedly whipped his 4-year-old son with a tree branch as a form of discipline.

I will never agree that spanking is the most effective way to discipline, although plenty of people I respect apparently do. I am sure I swatted my children's bottoms a few times when they were young, but these were not my prouder parenting moments. My actions were out of frustration, anger and a lack of control — which is why it was so difficult to watch others struggle with similar emotions in public.

Since that day in the parking lot, I have often wondered when it is appropriate to step in, and when to mind my own business. Parents are a particularly defensive lot, prone to immediately withdrawing into a self-righteous ball of "Don't-tell-ME-how-to-raise-my-kid."

Often, it's a parent's inaction that attracts criticism. How many times have we all secretly wished that someone would take their screaming child outdoors instead of ignoring a tantrum?

It feels intrusive to get involved. Even when giving advice that is not about discipline, parents may perceive attempts to help as meddling.

Once at the airport, I tried to warn a young woman whose toddler was playing alone near the baggage conveyor belt about what had happened to my son at that age. While standing right next to me, he had poked his finger at one of the grooves on the moving belt, which ripped off his fingernail within a few bloody seconds.

I had barely begun stammering out my good intentions before she marched away, conspicuously allowing her child to continue hovering over the conveyor belt.

Friends are divided on what to do if faced with ugly or seemingly neglectful adult behavior. Some say they will speak up, perhaps even ask the child if he or she is OK. Others offer a silent prayer and move on. Most prefer to look the other way, out of fear.

"I turn to my kids and say so they can hear, 'Aren't you glad I'm not like that?!' " said Chris Green Lang, referring to parents yelling at children in a store.

On the other side of the tantrum, Andrea Quintana said she has been that mom, not swearing, "but angry and not being effective."

"A bystander intervened with compassion and grace, and it was like cool water on me," said Quintana, who has a son with autism. "Keep in mind that the mom is already in 'fight or flight' mode. Judging, threats, criticism is just going to be gasoline on the fire and will help no one. If you can't find it in you to offer help and kindness, walk away and don't make it worse."

Some mental-health experts agree that, depending on the bystander's comfort level, the gentle approach works best. Asking an angry mother, for instance, if she needs help might be "just enough to stop the moment and use the situation," said Katie Conklin, program director at an organization that teaches behavior management for young children.

One social worker has referred clients to the agency from situations she's observed on the street, Conklin said.

"It's touchy, because you don't know how someone's going to respond," she said. "You have to make sure you feel comfortable to do that. … You have to assess the situation. If it is dangerous, you should call the police."

My son, Jesse, was 17 and working at a candy store in a shopping mall when he was faced with an uncomfortable scenario that still bothers him. A woman stood at the counter, with her toddler standing next to her. The child was understandably excited at the colorful display of chocolates and candy-covered apples, and began touching the glass that separated her from the treats.

The woman "kind of slapped her on the back of her head. It was pretty hard," Jesse said. At first he ignored the woman's action, but he became flustered after she picked up the child and hit her again, this time on the side of her face.

"I said, 'Can you not do that in here?' " he said. "It was pretty awkward. I didn't handle it very smoothly."

She asked him what he meant, and he was forced to clarify and ask her to stop hitting her child.

She retorted that she was not going to take a teenager's advice on disciplining her kid.

"I said, 'Can you leave then?' " said Jesse, who added that he was stammering at this point.

So she did.

I think he did the right thing.

As we watch the NFL attempt to redeem itself on its domestic abuse policies, I can't help but think we all need to speak up more often.

Lisa Black is at lblack@tribune.com.