It's necessary that adult put eyes on children while they play. Though some adults misunderstand this instead of playing the role of a supervisor they become judges and some even take children's matter too seriously when it ought to be treated as children's case. When you're child or ward is playing with other kids within his/her age bracket it's not uncommon to find out one whose hand is stronger than others or having a kid who is not a fighter could cry and it's not for an adult to take over the fight. Allowing the them to settle their differences makes them stronger but for weaker they might be if an adult always come in to settle their differences.
My experience
Today, I witnessed two parents who where into physical combat just because of children's normal play.
Why the fight every one asked, and one of the parent said her took my son's football. The children are of about same age 7+ and from the story of both parties, the ball was taken from the other boy out of play and demanded that they play together the owner of the ball said no he doesn't want any one to with him funny right? This is normal with kids . Now because the other boy insisted that they play together, the owner cried home and his mother didn't care went with her son asking for who beat up her son and took his ball and the son pointed at his friend and his friend and this woman manhandled the little boy and the little boy cried home and it's now the matter of adult.
Bullying isn't encouraged.
It's very true that some kids do bully others but it's better to understand play and bullying. No one would be happy to see he's ward being bullied.
It's also necessary for adults to understand that most children's play isn't hatred just war for supremacy. What adults should do is just act as supervisor not as a judge. Letting kids to settle their differences makes them better and when we are not there they will be able to settle themselves but coming into their matter always will make them always look for someone to settle their matter. This will make them to depend on others to making peace.
Some mothers are real mothers they have better understanding of children's life . This mother on the photo decided not to fight back but took her son home and told the other woman give children space to settle their differences.
Teaching the kids how to resolve their conflicts is the best.
As a supervisor, when we notice bullying, without delay we ought to address it properly and not taking over the children's place to fight .