when should adults step in when kids bully?

Here is something to think about now that the kids are back to school...
​I just finished reading a book with some interesting ideas to ponder on bullying... the book, written by Emily Bazelon, is called Sticks and Stones: Defeating the Culture of Bullying and Rediscovering the Power of Character and Empathy.
Here's thought #1
"Even though it's normal for adults to want to protect them from all meanness, or to rush to their defense, there's a reason why Mother Nature has promoted the existence of run-of-the-mill social cruelty between children.  It's how children get the practice they need to cope successfully with the world as adults."  Bazelon argues that dealing with cruel kids teaches you not to take goodwill for granted and teaches you what kind of behaviour you appreciate and want to give.  Being bullied helps you understand what someone else might be feeling when you see them treated badly.
The flip side, she admits is that not everyone bullies and when kids understand that cruelty is the exception, not the rule, they respond and bullying drops and students become more active about reporting it. (p13)

Thought #2
"By prying too far into the lives of teenagers, we impinge on the freedom they need to grow.  We stifle development when we shut down unstructured play at recess or censor their every word online, in the name of safeguarding them from each other.  We risk raising kids who don't know how to solve problems on their own, withstand adversity, or bounce back from the harsh trials life inevitably brings."  

Thought #3
Adults always want to see the bully get punished but is it fair to hold a child to the same standard of accountability as adults?  Adolescent brains are still developing, especially the parts that govern impulse control and judgement.  Shouldn't we be focused on giving kids a second chance?

Thought #4
Bullying online is a huge issue.  "In a 2009 study, researchers asked middle and high school students what would deter them from bullying other kids online, and the and answer the teenagers ranked first was parental discipline in the form of taking away access to social networking sites.  Second was taking away their computers or phones." (p263).  Point to be made is that parents have a duty to intervene to limit bullying.  Parental monitoring should be seen as a form of caring, not interference. 

We want to keep our kids safe and free from bullying but that's probably never going to be completely possible.  At the same time, make sure that your kids have the skills and understanding of the situation so that they can respond themselves and not totally rely on parents.