Generally, I let parents be parents and I often find it doesn't help to give a parent a suggestion on how to handle their children, especially if it's a tense social setting (Jr's pitching a fit in public for reasons unknown and parent(s) is upset and embarrassed by the event, etc...) I am childless and have no current plans on having kids but that doesn't automatically disqualify me from knowing what various punishments can do to kids. I say that because I vividly remember my parents' punishment methods, what I did in (most) cases to deserve it and what I've learned as a result. My parents were of the Spanking Club, 'Belt, Switch and Hand' chapter. Looking back, I've realized that getting spanked for something not only told me that whatever I was getting spanked for was undesirable but it also taught me that doing said undesirable thing needed to be done with more tact (no, I had no idea what tact meant at that age, but that's what it was.)
One example: I REALLY hated peas as a kid. Refusing to eat peas was not a good thing, but hiding the peas in a papertowel behind furniture (where they were usually forgotten about until they developed a personality) was Undesirable. So I was punished for and stopped doing that, but came up with a better way to dispose of unwanted peas. I got really good at hiding food in my cheeks without it showing on the outside or showing when I spoke, practicing with M&Ms, peanuts, etc. So...dinner's over, run outside to play, dispose of peas behind the shrubs. Parents never knew, I was never punished for it. And all I knew at the time was I found a way to continue defeating The Peas without getting The Stick. In this case, spanking taught me to better hide the evidence