“This is the sort of thing you can expect to happen if you actively resist security personnel on an airplane.”
No this is the sort of thing you can expect to happen in a Police State when people get their ass kicked by the police for doing nothing wrong and acting in a legal manner.
Refusing to leave makes you legally in the wrong. Police routinely have to escort unwanted guests out of people's homes and businesses, and the need to do so does not constitute a "Police State."
The wacko passenger was at fault
he disobeyed a lawful order to leave the plane. He violated several security rules by being belligerent and out of control after being advised to vacate the aircraft
The settlement is a travesty of justice