We don't know from the anecdotal evidence of a 15min parent child interaction what that Dad had been going through. Perhaps his wife had just died?
An example I have is that I know that my children will attempt to use those around me to manipulate me, the simple looking innocent when asking for a treat when they have already been promised something else. In front of others this places peer pressure on me, its not something that I bow to since its bad on me and my children. However from the outside it might look like I'm being mean.
This article tried to play on my emotions for going though what every parent goes through. The best parenting advice I could give would be that you should treat your children as Mini-me's. Do what's best for them as if they were you. Following that is all you'd ever need.