The problem with team sports involving kids is that the coaches are parents. The parents become too competitive and demanding and put an unwholesome emphasis on winning. One simple reform would enormously improve childhood sports: The coaches should be kids, too. Parents could be around in supervisory roles, sort of like the major league commissioner, but kids should run their own teams. Sure, they'd make mistakes and the level of play would suffer and, in fact, the whole activity would look a lot more like a Game and less like a Sporting Event. Kids become so co-opted by the adult obsession with winning that they can't just mess around and have fun.
I'll admit, at the beginning, that everyone has seen the stereotypically overwrought parent who can't seem to accept anything but perfection from Little Johnny/Jennie and his or her coach on the field. It does seem worse these days, especially with the high-pressure drive for perfect lives with perfect little children and soccer games and football and art classes and the perfect dinner too. I suspect that this drive for perfection in all aspects of life just makes the incidences of parents-as-sports-monster worse.
That said, I think he's wrong.
First of all, kids do get to "be their own coaches." Even in this day and age of parental hyper-concern over predators, and nerf-society concern over bike helmets and not letting Johnny out of sight, kids get together to run around, play games, bike, play kickball, and so forth. They set their own rules, choose their sides if any apply, and get to make a mess of things or not as they see fit.
This is an invaluable experience and provides them a chance to make mistakes and just mess around.
That said, there is a darker side. We all know the stories of the playground bullies, the kids who don't get chosen (or otherwise ostracized), and such, that without parental involvement kids have to deal with.
Organized sports with parent coaches doesn't just serve the purpose of parental supervision, it's an education. Sure, we can still have weak-spined coaches who don't shield the kids from their own parents, and jerks who are just as mean as the parents or play favorites. Even then they are more likely to be fair, or fairer, and push the kids to reach beyond themselves to new heights.
It's an education in sportsmanship, fairness, and teamwork that you will not get from other kids without a decent adult handy.