Punishment does not usually cause physical harm. Causing harm would be legally considered abuse. Not causing visible harm doesn't mean it's not punishment. The only reason it "gets their attention" is because it hurts. Or is at least uncomfortable, aversive in some way. On the learning quadrants, it falls under positive punishment. Own your actions. If you choose to use aversives in dog training, own it. Don't pretend it's something it isn't.The idea is to get their attention not to harm them
And your wrist is very different from your throat. Popping the neck with a choke chain briefly shuts off air flow, which triggers a survival fear response. If you believe in your actions, at least know the facts.
(Full disclosure: I took 4H dog training classes as a teen and found the methods to be very harsh and sadistic. They may have changed methods by now, idk)
Obviously she had to stop eventually, at least to drive home. Where does one draw the line? You don't know if she took him home and hit him 50 times or more. But someone agreed with her that hitting the kid was right, ya know? And told the guy who said she was wrong that HE was wrong. So now she feels vindicated :/. Not to mention that the other people in the store might be like me, even if not, nobody really wants to see/hear that kind of thing.The biggest difference between the two situations, as I personally see it, is that the woman in your store didn't stop
There would be no point in smacking a kid if it didn't hurt and/or make them afraid (or if it weren't humiliating or aversive in some other manner). Little kids are grabby. Their brain development is not at a point they can control that fully. If someone smacked their toddler every time they "deserved it", they'd be smacking the kid 100 times a day. Sadly some parents do that. I can't imagine how miserable it would be to be their kid.