They're individuals, they have shown free will and they are capable of emotion like being visibly shaken they had to nuke Ohara, plus lamenting the Vegapunk situation and questioning Imu's decision to nuke Lulusia before bowing down.
Saturn even considered sparing Bonney during his conversation with Doberman in the ship, before deciding she was too problematic to let go when she stabbed him and showed her knowledge of Kuma's memories.
They're just very loyal to their duty to keep the status quo and obey their liege Imu at the end of the day.