1. Should've handled the booking problem at the gate.
2. When they didn't handle the problem at the gate they should've doubled the amount offered to get the guy or someone else off the plane.
3. They should've handled the problem themselves instead of handing off their problem to security guys.

Legally they were allowed to rip the guy off the plane kicking and screaming but it doesn't look that great from a PR standpoint and it costs them a lot more money doing what they did when it could've probably cost them $400.