I would suggest the local buck stops at the station manager; nothing to do with the captain. The orders to the S.M. would have come from 'mission control'. The SM was "only obeying orders, m'lud". My question would be who authorised/coordinated the use of 'unnecessary force'. Was that a decision made on the spot by the bouncers? If UAL had said "create seats at all costs," then that is the fault. If the bouncers went beyond their remit, and should have backed off, then that is their fault. Someone has to discover who made the decisions to man-handle the pax in such an extreme manner.