The CMO is not a line officer but due to the idiocycracies of their authority they have a lot of power and authority when there is a medical emergency and I believe this qualifies as a medical emergency and the CMO is every right to give a legal order and expect it to be obeyed.
The risks the CSO took with the shelters and sickbay were not taking the initiative they were plainly stupid. There are a hundred ways to get to engineering without pulling off stupid stunts and as CSO he must have the manual override codes for the weapons locker. Basically he made a very bad call and deserves to be punished. Calguard saving the ship can justify risking lives but not if there are means to save the ship without risking lives. Anyway from what I see the ship wasn't in danger and the CMO could have well saved the day much sooner if the dumbass hadn't cut the power.
There is a very fine line between heroism and stupidity and well I think he crossed and and well pay the price.
Arise, arise, Riders of Theoden!
Fell deed awake: fire and slaughter!
Spear shall be shaken, shields be splintered,
a sword-day, a red-day, ere the sun rises!
Ride now, ride now! Ride to Gondor!
Theoden King: The Return of the King