Interesting thoughts you have there. :-)

This is a difficult one to go about, I don't think being an only child is the main cause for this kind of behavior. I recognize the behavior you describe but in my son's class the one kid that stands out negatively has two siblings (just an example).

Then again, if a child is already displaying negative behavior it can be a difficult process to replace this with more socially acceptable behavior. As fellow parents you can exchange advice, but I would never put myself in the position of being an 'expert' on resolving such problems. Maybe more like somebody that is speaking out of experience.

Besides that and perhaps a bit off topic, I think schoolyard gossip is a very passive and overall negative way of tackling a problem, but that's just my point of view...