There is even a market for blood itself, with the strange stipulation that in the US the donor isn't compensated. (But everyone else along the supply chain is paid handsomely).
I appreciate where you are coming from - It seems like you're saying it's not that far from existing common practices.
But if people find something distasteful and think it's a bad idea, how close it is to other things isn't really relevant. Maybe those should be banned/fixed too, maybe not.
But if people dislike something or find it "yucky", it's fair for them to raise objections.
I used to work in that field and it's actually a great stipulation. Otherwise you'd have poor people coming in to sell their blood to make a living. The place I worked at paid people for plasma (but not for whole blood) and it was a difference like night & day in terms of the kind of people that this attracted. They often came in as often as was legally allowed (every 10(?) days) and looked awful.