Could you elaborate, including what the consequences of such "overdiagnosis" might be?
I don't claim any expertise here, so what I've got are personal perceptions, not empirical evidence.
Kids are going group together with certain other kids, and exclude still others. I also believe that kids develop their means of communications, as pointed out by shakeysix's anecdote.
I am still being kidded by the kids about the seemingly serious girl argument/locker slamming scene that I broke up the first week of school, a couple of years ago, because it turned out to be horseplay. Grumpy Mrs. Smith wades into the crowded hallway spouting Hippie platitudes about harmony and tolerance while the whole Freshman class is cracking up because the girls calling each other Gringa and Greaser are really best friends. Nice first meeting with the entire class. The principal had the girls in tears before we realized I had over reacted.
I looked like an idiot to the kids and with good reason. Although I drug them to the office, Estefani and Katie-- the Gringa and the Greaser-- have turned out to be good students and good kids--although not as respectful to an old cranky teacher as I would like. It was a snap call and I called it badly.
As much as we might like to prevent a child from being "left out," it happens, and always will. It's heartbreaking to watch the Down Syndrome girl be rejected. And it adds to the hurt when it happens
en masse like happened in the video.
But rejection, in and of itself, is as much a part of life as breathing. We're all here (at least in part) talking about a pursuit of something that is 99% (or more) rejection.
A group of people can discuss and decide without intending harm. In fact, they've done no harm just by saying no. But bullying has to be more than that, doesn't it? More than saying no, even if said badly?
If we don't give these children the right to say no, what's left to them? Beating up the girl before she gets close enough to ask? Running from her like she has The Plague?
Socialization isn't an instinctive process. Well... not entirely. Nor does it always take place in the way we'd wish. To some extent, if we are too quick to judge negative responses as bullying, we actually shut down communication (and respect). The exact opposite of our intention, isn't it? Very much like just about any other zero-tolerance attitude, I'd argue, it achieves the exact opposite of the intended goal.