I wonder how many correspondents on this thread are parents? or even remember what it is to be a child?
I see lots of bad parenting in daily life, kids eating McDonalds & turning hyper for hours, lack of control by parents and so on, but children are not necessarily reasonable creatures.
My 18 month old toddler has at her stage of development, limited emotional responses, so conflict can produce tantrums. Regularly.
There are coping mechanisms for this, such as distraction and ignoring the problem, but in the confines of an aircraft, these can be difficult to apply succesfully and they don't come with guarantees. A little perspective would help, there are two sides to every situation.