> Your argument might satisfy a peculiar revenge fetish
A "peculiar revenge fetish" is strong words considering your argument is so weak.
> the whole public is only healthier if the WHOLE public is healthier
In general I agree, but this is definitely not an issue with transplants. The demand far exceeds supply, so the question is how you sort the queue.
Of course, refusing to be a potential organ donor also affects the health of the WHOLE public. If you refuse to be a donor, the total number of organs available for transplant is reduced.
> people who are ineligible to donate (like under age 18)
Where did you get the idea that under 18s are not eligible to be donors?
I think everyone would agree, though, that under-18s' views would not make them ineligible as recipients.
> unwilling sacrifices on your altar to Fairness
If it's not them who are getting sacrificed on the Fairness altar, it is someone else who could be a recipient.