14 Dumbest Things In Star Trek The Motion Picture
13. Kirk's Dickish Decker Demotion
KIRK: I’m taking over the center seat, Will.
DECKER: You’re what…?
KIRK: I'm replacing you as captain of the Enterprise. You'll stay on as executive officer, temporary grade reduction to Commander.
As Daffy Duck has said, “Is this trip really necessary?”
“Ship’s captain” is a job, not a rank. You don’t have to hold the actual rank of captain to captain a ship. Commanders can do it. To invoke Star Trek’s 60s contemporary Voyage to the Bottom of the Sea, Kirk could play Admiral Nelson to Decker’s Captain Crane. Kirk in charge of the mission; Decker in charge of the ship.
So actually demoting him is, to use Decker’s word, “unwarranted”. You think that’s not going to look bad on his service record? There’s no good reason for Kirk to do. He just wants to be “Captain Kirk” again, so he’s literally screwing Decker over to get his wish fulfillment. He’s just selfish and cruel, and even when he starts to see the error of his ways, does he make amends by giving Decker his rank back? Nnnnnope.
At the very end of the movie he tells Uhura to list “Captain Decker” as “missing”. A little late there, Jim.