Well, if my 6 year old was tearing things off walls and attempting to hurt other people, yes I would want my child restrained.
According to the article, the police officer attempted to reason with the child. If the child continued to be wildly destructive and throw things, what else could the cop do? Put her into a bear hug? Is that so much more humane than cuffs?
Oh, and one more thing. If it were my child, I would not be angry at the cop. I would be embarrassed at my failure as a parent.
Bingo.