I think it is good to feel strongly about an issue. There is nothing wrong with being angry and hot-headed about anything of importance and it is certainly better than being ignorant or cynical or just not caring. But I also think it is necessary to use cold reason to analyze and completely understand a topic one cares about.
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.
This is what we humans have a problem with, a catastrophe that has no deeper meaning. We are very good at coming up with reasons for something horrible that happened (Pat Robertson and 9/11, euphemisms for being no more like "resting in peace", the ancients sacrificing something to the gods to influence the bad weather) but we have a hard time embracing the total lack of sense of something like the Tuvix accident. There was no higher power involved and there is no meaning to it. Two people die and one was born. It is a total nightmare.