I assure you none of the people here harping on him for disciplining the child ACTUALLY HAVE CHILDREN. Its so easy to be politically correct from the sideline rather than watching your child grow up to be a cunt because no one ever drew a line for them because Dr. Spock says hitting isn't nice. Some kids just aren't nice to begin with. Believe it or not serial killers, wife beaters, rapists, and muggers were once children too. I would argue they received less discipline than more, and clinical trials tend to support that given children without fathers (traditional administer of discipline) are more likely to end up in prison. Its not like he is BEATING the child or even spanking him for his own enjoyment, he has tried being "nice" and it is not working. IMO not disciplining the child is a form of neglect he and many others will pay for in the future so that everyone involved doesn't have to make hard choices.
Additionally the atmosphere in schools today is very hostile, they are charging small children with crimes now as simple as hugging (sexual assault) and hitting (violent assault). Which is more traumatizing to the child, getting spanked when he hurts other people or being dragged off to the police station one day in handcuffs by a strange adult they don't know? (yes they handcuff children).