As a radical libertarian, I wouldn't be much at home in any kind of dictatorship, and no one I've ever met or read values freedom more than I. Freedom - which I define as freedom from coercion - includes the right to protect oneself and one's property, and to use any means necessary (including lethal retaliation) to do it.

The girl was in no way innocent; she simply hadn't been tried and convicted, so the law presumes that she may be innocent. "Not guilty" criminal verdicts don't imply innocence; they simply state that the state did not prove its case beyond a reasonable doubt. There is no dispute concerning the violence in which she had already engaged against an adult. She was out of control, and her hands were where they shouldn't have been. Perhaps she was no danger to the police officers' lives, but she might have intentionally hurt them physically, however slightly (the degree is irrelevant). That's not something they have to tolerate.

Are the officers above reproach here? Not necessarily. Perhaps if they'd restrained the violent brat better beforehand, she wouldn't have been able to get her hands in front of her. Perhaps they should have cuffed her feet, too, and used better restraints. That's a matter worth investigating, surely. But restrained or not, the girl wasn't simply kicking the car; her hands were in a dangerous position.