I've been watching Voyager for the first time and just got to the episode. I think I agree with the decision (as a lever-puller) but it does raise some interesting questions. As Janeway mentions, if they'd been able to do it immediately, she'd have done it without question, but after two weeks of Tuvix integrating with the crew it's a more difficult question. If Tuvix had been around for say 5 years I think I'd disagree with separating him. I think the way I look at it is that the social bonds possessed by Tuvok and Neelix are more important than the mere two week old bonds of Tuvix, but if Tuvok and Neelix were long dead and their loved ones had already mourned them, while Tuvix had had more time to become a fixture in people's lives, then the circumstances would be different. Tbh I disagree with the idea that Tuvok and Neelix get the biggest say - I think that the input of Kes and the rest of the crew is valuable, and Kes pleads to get Neelix back while none of the crew back Tuvix.

Does that mean the worth of lives is based on popularity? Not generally, but I do think that social connections are a relevant thing to consider. Part of what makes murder bad is not just the loss of the individual's life, but also what it means for everyone else. If you could press a button to create a life then press another to end it, would you have made the world a worse place by doing so? I don't think so. But if you press a button to create a life then go out and murder someone who already existed, then I think you have.

I'd also say that the captain's responsibilities in her role as captain are relevant and also support the decision.