One day I was with my daughter (~24 months old) at the Zoo and she wanted an Ice Cream and I said "nope". She looked around with wide eyes and noticed all the people near by. Then, she did something I had never seen before -- she dropped down on the ground, twisted and swirled, and started to scream; for quite some time. I calmly sat down nearby and asked her: "when you're done, could you let me know?". Over the next minute or so, several parents gathered around to gawk at the spectacle. When my daughter got close enough to some urine on the ground, I got up, walked over and said: "careful, icky pee here". Without stopping the rolling or the screaming, she immediately recognized and steered clear of the urine. I then sat down again and said, "when you're done, could you let me know?". After another minute or two longer, with hoarse voice and a few bruises, she stood straight up and said: "Fine; I'm done. Monkey next?".
What was problematic was the reaction of other parents. During the episode, they became increasingly anxious looking at each other and trying to catch my attention. One of the mothers asked me "Where is your wife?", to which I responded: "at work, but don't worry, I'm the primary care giver". A father said (after being nudged by his wife): "well, you're just going to sit there?" to which I calmly responded: "It's a temper tantrum". One final mother didn't say a word, but made sure to give my daughter comforting eyes and looked harshly at me, making sure I knew she was dialing someone (police?) on her cell phone.
Once my daughter got up, we inspected her pants for horse urine and talked about how that was an extreme waste of time. Later on I asked her what the Tantrum was about. She explained it quite clearly to me: "well, daddy, one other boy just had one and he got the ice cream, so I wanted to see if that would work". I explained to her that this was pretty bad behavior and that if I ever see it again, we will go home immediately. I've had a few tantrums since, but none of them have been public. My daughter and I then had a very fantastic afternoon talking about Monkeys and more effective ways to communicate her desires.
This was a very unexpected experience for me. I seriously didn't expect that in 1-2 minutes, I'd have a dozen adults gathering around in a circle. I didn't expect 2 of them would be brave enough to hurl insults. I didn't expect one of them to be implicitly threatening police (CPS?). I can see how many parents would have caved under such peer pressure. Perhaps it's not the parent's fear of the children that leads to these problems, but instead, fear of what other parents might say or do?
So. I'm not sure how to connect this to this thread. First I'm not sure a "rule" would have helped. Punishing her wasn't going to help (I evaluated going immediately home, but I think the event was traumatic enough for her already). I'm not sure. Would you do it differently? If you saw me on the bench, would you think that I had given up?