• Why is kids picking up on 'inappropriate behavior' appropriate?

"The social group basically polices itself and enforces the rules of social dominance, the social morays of the troupe, and monkeys who don't pay attention to those rules -who are overly aggressive in their interactions- don't last in that troupe very long. They're kicked out of the troupe. They go solitary and most of them don't survive." –Steven Suomi, Origins of Human Aggression, YouTube

Paraphrased, if not outright stolen, content:

Play fighting is as natural in humans as it is in other animals, but guardians often forbid it, because they see in play fighting disturbing signs of violence. It is however, extremely useful to a child's development.

"By competing physically with others, the child discovers who is stronger, where each person's limits are, and whether aggressive acts are acceptable. Play fighting also requires compromises. The strongest must learn to let other partners win from time to time, or they will find themselves without playmates. In fact, as shocking as it may seem, play fighting apparently teaches youngsters to control their aggressive behavior."

The desire and pleasure of being part of the group, forces a child's brain to develop ways of regulating anger. "Discipline plays a vital role in eliminating aggressive behavior" and is beyond the scope of this question, but it is expertly discussed in the video. Preventing the recurrence of this behavior through discipline is much more desirable then the solutions that are commonly used for those of older age, and usually as a last resort:

Removal or 'special placement' of individuals with aggressive behavior has disastrous consequences. "They never learn desirable social behaviors and even worse, by a sort of mutual contamination, encourage one another to maintain their violent behavior."

"Children who fail to learn alternatives to physical aggression during the preschool years have many problems." - Think long and hard about, how or of what you "censor" for your children. Above all, be consistent and never divide the parental unit (play fighting aside, I can only assume WWF-dad wasn't helping the coherency of the unit).

• Why is kids picking up on 'inappropriate behavior' appropriate?

"The social group basically polices itself and enforces the rules of social dominance, the social mores of the troupe, and monkeys who don't pay attention to those rules -who are overly aggressive in their interactions- don't last in that troupe very long. They're kicked out of the troupe. They go solitary and most of them don't survive." –Steven Suomi, Origins of Human Aggression, YouTube

Paraphrased, if not outright stolen, content:

Play fighting is as natural in humans as it is in other animals, but guardians often forbid it, because they see in play fighting disturbing signs of violence. It is however, extremely useful to a child's development.

"By competing physically with others, the child discovers who is stronger, where each person's limits are, and whether aggressive acts are acceptable. Play fighting also requires compromises. The strongest must learn to let other partners win from time to time, or they will find themselves without playmates. In fact, as shocking as it may seem, play fighting apparently teaches youngsters to control their aggressive behavior."

The desire and pleasure of being part of the group, forces a child's brain to develop ways of regulating anger. "Discipline plays a vital role in eliminating aggressive behavior" and is beyond the scope of this question, but it is expertly discussed in the video. Preventing the recurrence of this behavior through discipline is much more desirable then the solutions that are commonly used for those of older age, and usually as a last resort:

Removal or 'special placement' of individuals with aggressive behavior has disastrous consequences. "They never learn desirable social behaviors and even worse, by a sort of mutual contamination, encourage one another to maintain their violent behavior."

"Children who fail to learn alternatives to physical aggression during the preschool years have many problems." - Think long and hard about, how or of what you "censor" for your children. Above all, be consistent and never divide the parental unit (play fighting aside, I can only assume WWF-dad wasn't helping the coherency of the unit).