The problem with a 'group bullying' scenario, is that all individuals did, is voice an opinion. One or two exchanges. Individually they will never see themselves as bullies, because they DIDN'T bully, right? They will forever be blissfully unaware of the effect they had in contributing to the pile-on. They will always see their actions as individual, never as a group. The internet is ground zero for faceless, harmless, opinion contributions, that add up to a disgusting spectacle of group feeding frenzy. And that's the adults willingly participating on here that come to mind. I can't even fathom what it looks like with the emotional teenagers who want no part in being the object of discussion.
When I was 14 I was slapped around pretty hard by a group of bullies in a school washroom. The entire incident went on for about 15 minutes and I was only able to try and block the repeated blows that resulted in my face looking like a lobster shell after being dropped into a pot of boiling water. After the incident I felt humiliated more than anything. That was my only issue with these bullies, who moved on to Senior High and presumably a life of crime after that and I went on to do my own thing.
Another incident I would attribute, was an NCO who used to hit us with his drill cane if we touched the wrong side of the gun sight on a howitzer. To strike back meant military jail and worse, forfitting my opportunity to become a soldier. I did do one thing, I swore that one day I would return to that recruit school and never put my hand on a man to correct him. I also made sure that no soldier would ever be afraid to approach me with an appeal for help if they were not grasping something I was teaching. I kept both of those promises and for all the pennants, gunnery trophies and accolades it was the greatest and most fulfilling achievement of my career to have a group students thank me for that dedication.