Here is an all but equivalent example: you have two terminally ill patients - alive in a very real, indeed, literal sense.
They will be dead* in a month if you do not find a heart for one and a whole liver for the other.
If you kill another person and chop her up for heart and liver, you will save these patients.
You actually think killing a person to save these two patients is justified?
Or that watching the patients die (or slip into a coma) because you cannot save them (without killing another person) is murder?
*or they will slip into a coma - if you want to be medically unrealistic, as the star trek situation is.
Sorry to chime in here - especially since I don't think Janeway's decision was right - but your example is really *not* an equivalent to what happened in "Tuvix".
Most importantly, Tuvok and Neelix were dead by the time Tuvix came to life. There was no other way to revive them than to kill Tuvix. In your example, your two patients are still very much alive, and a lot can happen within a month, another donor could be found etc.
In the episode it's pretty much directly stated that Tuvok and Neelix are alive somewhere inside Tuvix - AKA they can be recovered 'alive' if you kill another person.
Also - there's a chance that another donor will be found within a month for the patients?
Well, there's a chance that a way will be found to recreate Tuvok and Neelix without killing Tuvix - during the rest of Tuvix's natural life.
If anything - considering the trek tech and the large time span - this chance is far larger than finding a donor (AKA person who just dies and has compatible organs; plus, there is the so-called 'waiting list') within a month.
So, no need to go to drastic measures and kill a person just for the off-chance that he/she's a suitable donor for *both* patients - let's not even mention the legal implications here.
Straw-man - the person killed will, of course, be compatible with both patients - AKA his/her murder would save the life of both patients.
As is made pretty clear in my previous post.
And the 'legal implications' are present because law-makers, unlike trek fans vis-a vis their fictional hero, actually see the moral of the situation for what it is, as opposed to grotesquely distorting it.
I'm a medical doctor, so forgive me but your example really lacks any similarity to Tuvix's situation.
Baseless rhetoric and obfuscation attempts won't change anything to the two examples being all but equivalent.