The precedent is the deliberate action to kill (the scientific literature uses the term "destroy") the embryonic human for the purpose of research and possible benefit of others. There is no approved precedent for these sorts of actions. The medical and scientific community for the most part, has rejected the findings and use of the results of Mengele's experiments and the Tuskegee experiments. It is currently illegal to use US Federal funds to act to destroy human embryos and the European Union and the Nuremberg Code have uniformly condemned any use of non-competent humans in experiments that have no hope of benefit for the research subjects. Parents may not ethically consent for their living children to be used in even harmless experiments if there is no hope for the individual child's health to be improved. None of these ethical codes and none of the laws of Western nations will allow for one human to be killed for the benefit of another.
If this line is crossed, there is no reason to condemn China for picking certain prisoners for use as organ donores or for picking specific people to become prisoners for the purpose of using them for organ donors.
It does not matter that the embryos are frozen, the fact that they are humans, and that they will not benefit - even without the inevitable, intentional loss of their lives.
The ones who caused them to be and then who caused them to be frozen should be held to the same standard as any other parent or guardian. At the very least, "First, do no harm." If nothing else, they should be maintained in the freezer until natural death.
I see your points. Thanks for the discussion. To me this a difficult question. I would rather that they use the embryos for creating a child but if they are never claimed and spend eternity in the freezer is that any different than letting them die? In both cases they are not allowed to come to fruition as a human being. Morally I see no difference. Who owns the embryos? The parents that have never claimed them? What happens if the parents die? Can they donate their embryo to science? A lot of questions and conflicting ways to look at this issue. For me, anyway.