It's even worse than that. They were disembarking passengers to make room for their own staff who were not even planned on this trip.
They had better alternatives: other customers had offered to leave for higher voucher value, I'm sure they could have paid someone already in Louisville 4x overtime. Instead they chose force and intimidation.
So you're saying, unlike doctors, flight staff are demigods and must be given priority because they are irreplaceable?
(The funny thing is, I'm pretty sure United will view their flight crew more as cogs than demigods.)