Tuvix murdered Tuvok AND Neelix! Janeway just unmurdered them, and didn't even violate the temporal prime directive! Fek'lhr's sake, will any conflict resolution ever make you people happy!?!?!?
Tuvix was not responsible for the circumstances of his birth. Unless you want to start arresting babies when the mother dies during labor.
The deaths of Tuvok and Neelix was a tragedy but what Janeway did was as immoral as murdering a person to use his organs for transplants to save his parents.