Re: Janeway's Decision to Kill Tuvix
I see it as equivalent to any other Trek episode where a crewman is taken over and controlled by a noncorporeal being. Any captain would have tried to get his crewman back. For Janeway, two of the crew were being controlled by a single entity.
Dr. Howard, Dr. Fine, Dr. Howard: For Duty and Humanity!
--Men in Black, 1934.