Presumed consent is an oxymoron. If it's presumed, it isn't consent.
As a concept, introduced in law, it's very worrying.
Trying to think of another scenario where a person might say "but I didn't consent, at all" and the law saying "don't care, you never said no either, so we took your silence to mean yes".
In a rape scenario feminists have argued for years that lack of a "no' does not equal a 'yes'.
I don't want to see any precedent of 'presumed consent' entering our legal system in relation to bodily autonomy, ever. So the development disturbs me.
I was one of the minority who was on the opt-in register; statistically it is likely that most of the people lecturing you OP, will be doing so from the dubious position of never having bothered to register themselves whilst the register was opt-in. I'm not sure someone who, even now, ISN'T registered whilst explicit consent is still required, has the moral high ground to lecture you when a dodgy principle of the state owning rights to your body without your actual explicit consent being needed is introduced.
I am still a willing organ donor. But I am no longer on the register because I will not passively support any 'presumed consent' system.
If I die my next of kin are aware of my willing donor status. In effect, as long as the donation service treat my body and rights as a person with respect, and seek to ask my next of kin, they will still have my organs.
It's a great shame they no longer have the absolute certainty that I have offered, of my own free will to be a donor. My presence on the register once was indisputable evidence of my wishes. Now the register is no longer is a record of those people motivated and certain of their own consent.