Guys, we're not saying every toddler can take on 2 armed policemen and walk away victorious with a trophy ear between his teeth...
We're trying to explain that if things did go wrong, and bad luck happens, then a small kid who's in a rage, and strong enough to tear things off a wall, could POTENTIALLY do damage, and police have to deal with potential threats and make them not a threat any more.
Personally if they could make some kind of raygun that instantly caused extreme, agonizing toothache in every tooth, but did no actual damage, I'd be fine with them using it on anyone from 2 to 102, IF there was a risk of permanent injury to innocents.
Pain is temporary, injuries can be permanent. IF you have to explain to the kid why his eyes hurt, you say that the policeman had to protect the other people because he wouldn't listen, and so had to make him hurt for a little bit. Then to remember next time that if he stops, it won't happen again.
Of course the police should be responsible when using pepper spray, tasers, etc, but if there's potential threat, take em down without injury.
The idea that we should use kid gloves and protect the children, only works if we have children that are not wild, angry, and violent. Not all children are perfect little darlings, and I wouldn't advocate going into a library and randomly spraying quiet, well behaved kids.
He was acting like a violent, criminal midget, however, so he had to be treated like one, and they cared enough about his welfare not to use anything that could injure him. Again, pain is temporary.