I suspect that bullying is nature and nurture. I don't have much support for this, but I would suspect that establishing a pecking order is pretty deeply ingrained in our species in much the way you see wolves or gorillas do the same.

I grew up in an blue collar auto workers neighborhood until I was six, and after that spent weekends, holidays and other time in the same neighborhood till I was twelve. We were total fucking savages. Fist fights happened often, several times a week. Emotional, physical, mental torture was a daily occurrence. Generally we were having fun, but it was rough fun.

A kid comes home with a bloody nose, their parents would patch em up and send them back out. No one was looking to lay down any justice, us kids had to work out the social consequences of our violence among ourselves.

We mostly played away from supervision, in the nearby woods, the gravel pit, or just in the back of a yard. Occasionally parents would witness some exceptionally vile behavior and wade in to lay down some law. This was where things would actually start to get ugly. Kid would get snatched up and shook, smacked or screamed at. Mostly just the worst parenting techniques you have ever seen, but not performed by the kids parents, rather on their neighbors kid.

I was spared punishment from my neighbors fathers as my dad was feared by most the guys who worked the line at GM. The one time a father started screaming threats at me my dad was on the other side of the tall wooden fence. My dad popped over tossed and pinned the guy against a fence, arm on his neck, said a bunch of scary shit that none of us kids would forget for a while.

Anyway, total fucking savagery, stuff I don't even care to put in writing. This is the nurture side of things.

I might be wrong, maybe there isn't a nature aspect. I now live in a gentle city, filled with mostly gentle people. When I take my kid to the park to play I watch the older kids and am amazed at their soft considerate kindness. They are nothing like we were. They play without malice, I don't see violent themes in their play, they pass by my small child and say things like "oh soooo cute" and give her a soft pat on the head. It blows my mind. I worry that my child will grow with no steel in her heart, be unable to take the harsh blows the world delivers to us all. I wonder if I am just a survivor of something I shouldn't have been exposed to? I feel like I had a hell of a good time as a kid. Running wild with the only boundaries being how far I could ride my dirt bike (actually I wasn't allowed to cross certain busy streets that bounded two sides of my neighborhood, but we had a pretty wide range, and slipped cross that street on occasion). I could get my nose bloodied and go on with my day, none the worse of ware. Our games were our games, we had our own little child civilization, It's something I really value now, it's something I don't see many kids today having.