The girl was hitting her mother. Why should 60 other people (or however many were on the plane) miss their connecting flights or be late to meetings and so on because one uncontrollable kid. If the flight took off without the kid belted in and something happened to the kid, you know they would've sued. Here's a clear case where the airline was damned either way.
These young parents nowadays think their kids are little gods.
I have heard that, and that the kid was out of control.
IMHO - it was the parents who were out of control...