They say paying donors puts them & patients at risk, because it would stimulate donors' to lie about their health when donating and we can't be asked to test blood for everything. And the say it is unethical to pay for human tissues.
Except when they are selling it ;)
People have diseases they don’t know about and if people are ashamed by a disease, they’ll lie even when donating.
I just shuddered thinking that donations wouldn’t be tested.
Both of the key claims do seem to have evidence to support them:
1) Paying for blood shifts the socioeconomic distribution of the donor pool.
2) The socioeconomic shift results in more contaminated blood due to greater incidence of drug use and/or related blood-borne diseases that cannot all be tested for with high accuracy.