If this causes more people to donate, it's probably a good thing overall, even if the people doing it are doing so in the hopes of cleansing their own system of these chemicals.
We could also say that given a choice between death and HIV, the blood recipient would still want the blood.
…yes?
With respect to PFAS, which is a general societal/environmental issue it's likely that all donated blood has roughly the same PFAS levels, so recipient either gets blood with PFAS or no blood at all; and the "new" blood might have slightly more or less PFAS than the recipients current blood, but the recipient already has a comparable level of PFAS anyway.
The thing is, donated blood is always in short supply. you dont have much choice, when you have a serious blood-loss.
edit: I would be very angry if sombody would have chosen to use hiv blood on me while I was uncounciuos. Similar to how I would be angry if my arm would be amputated, while my conciousness was away.