The Doctor wanted to crack One's skull open like an egg to get his mobile emitter back. That kids life was massively less important than the Doctors freedom from sickbay "momentarily". You all keep going on about the sanctity of life. If Tuvix had erased the doctor's program, he would have been fine and the murderous procedure that was going to kill him would be lost to Janeway along side her incredibly valuable EMH. Would Tuvix have been put trial for murder of a hologram, or court martial for sabotage? The didn't cut his security privileges, and look how easily the Doctor MURDERED the EMH from Equinox. It would have been a piece of piss.