Or maybe they unthinkingly and blindly accept anything negative they hear, regurgitating it with confidence that they could not possibly be mistaken because it confirms their biases and validates their life choices.

Those too, but I find myself at a loss as to whom to compare them to in the context of elementary school. Maybe the kids that still believe in Santa by graduation?

There should probably be a citation here. Even if it's true, I don't know how this is relevant--I was bullied by a lot of people when we were children, but I don't imagine that they are still bullies today because people often mature in adolescence and early adulthood.

Where did you hear about this?

He made it up.