Perhaps I am stupid but I fail to see in what way the Tuvix accident is related to organ donation. It's not like some evil doctor took Tuvok and Neelix and cooked a Frankenstein monster out of them. It was rather an accident that happened without the involvement of any agency, it was a symbiotic plant getting into the transporter.
I don't think you're stupid. I'm at a loss, myself, and I did my medical ethics thesis on the ethical issues in organ transplantation. Granted that was back in the mid-90s, but I've remained fairly up to date on the technology involved and the ethical issues. I have made reference to live donor transplants, but that's the only place I see any possible correlation, and the argument would benefit Tuvix.
It is, as you say, an episode that puts Janeway in a no-win situation. And the thing is, she knew it
. Look at her face at the end of the episode. She's not clapping Tuvok & Neelix on the back and smiling broadly at their return. She says a curt, "Glad to have you back" and walks into the hall where she pauses with a look that says the entire weight of the universe is on her shoulders.
She isn't happy with what she just had to do. She will, however, live with it.
Tuvok is an organ.
Neelix is an organ.
Were they donated?
Were they stolen?
(Maybe it's comparable to being switched at birth?
Can you blame the mother for loving the wrong baby, or the children for stealing each others toys and crapping in some one elses diapers?)
But Janeway retroactively decided that because "Tuvix could not speak for Tuvok and Neelix" permission for the hybrids conception, and the continued re-ratification of their ongoing existence, would never have been given if the two original components had been allowed to decide for themselves before the meld and then periodically after integration to weigh if Tuvix is worth their deaths and then periodically ad infinitum still worth their deaths.
No permission = stolen.
(Why am I thinking about a mother refusing to breast feed because they're sure that their baby is an asshole?)
"It's easier to say sorry than please."