So you are ok with murder then?
Tuvix was a sentient being, and in a sense born on a Federation Starship which would make him a Federation citizen and as such entitled to all the protections that come with it, and even if he wasn't a Federation citzen when onboard a Federation ship, Federalion law applies. Murder is against Federation law. Therefore Janeway was wrong and is guilty of murder.
It isn't murder though. She is fixing a horrendous accident. I think that is where some people are mistaking the real issue and viewing this as some moral, murderous wrongdoing.
Here is a controvertial statement: Tuvix isn't real. He is a scientific accident. Tuvok and Neelix are real and their bizarre fusion has resulted in a hybrid mess. Is it sentient? Surely it is. However, is it a being? No...its two. [As I say with lives and careers, friends, hopes, dreams].
I find it deeply immoral to just leave Tuvix to exist. Its condemning two real people to die. For me, Janeway had the guts to make the right call when her supposed supporting officers washed their hands of an awkward problem [and had no problem welcoming back Tuvok and Neelix].
Claiming Tuvix had rights, or was 'born' on the ship is just...odd. He is an [easily] fixable transporter accident. 'He' is not actually real, he is two other people.
Janeway was right.