Agree. Some here, who may or may not have kids or have experience dealing with kids don't seem to understand the realities of kids. Maybe taking it easy on the kid is the best way for the parent to mitigate the bad behavior. Would you rather listen to a parent yell "sit down, shut up!" 1000000 times on a 6 hour cross country flight? Or give em a whooping then listen to the kid screaming and crying incessantly for 5.9 more hours? There are worse things than boisterous kids.
Maybe some of our fellow posters should consider taking alternative modes of transportation that aren't public - like a private car or private chartered plane/jet - if they don't want to be exposed to the vagaries of traveling with the general public on a common carrier.
That being said, sometimes I wonder if our legal system should give amnesty to allow us to smack around fellow idiot passengers. Just a little bit, of course, only to the extent necessary.