All it proves was that the dilemma itself is effective.
The episode and its resolution are crap, because they don't justify her decision. They leave it to the viewer. They do a disservice to everyone involved.
If someone's heart stopped in a hospital, then an alien possessed their dead body and said "I was just born, this is my body now, your guy was dead" I don't think anyone would argue that the person's heart could very much be restarted (assuming otherwise healthy) and the alien has no right to use someone else's bits.
As for the overall "did she do the right thing or did she murder tuvix", I believe she did both.
If my wife were to be blended with someone else like that, and the new identity begged me not to push the transporter button and murder them to get my wife back, I'd summon all the energy of Inigo Montoya and yell "I want my wife back, you son of a bitch!" as I pushed them onto the pad and smashed the button hard enough to crack the panel.
I fully recognize I essentially murdered a consciousness in order to save two others. And I can live with that.
If someone's heart stopped in a hospital, then an alien possessed their dead body and said "I was just born, this is my body now, your guy was dead" I don't think anyone would argue that the person's heart could very much be restarted (assuming otherwise healthy) and the alien has no right to use someone else's bits.
A better analogy would probably be, if an alien used the body of a cryogenically frozen person that we KNEW could be revived with 100% certainty.
Tuvix wasn't some alien body snatcher who possessed the bodies of the deceased. He was literally Tuvok and Neelix living on in a new form, which comprised a third entity.
In killing Tuvix, Janeway also murdered both Neelix and Tuvok.
What she did, in essence, was to murder three people to bring back two.
There being a method of resurrection doesn't make a person any less dead. They were dead, but Janeway the necromancer knew how to bring them back to life. All it took was a sacrifice.
Patterns merged, both wholes remained whole they just mingled together in such a way that created a third party. Tuvix is quite literally a schizophrenic fever dream for both originals..