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.
There is no conflict in light of inalienable human rights.
In the hard cases (unfortunately not rare in these days of IVF, just as predicted by Kass and others in the '70's), 2 wrongs do not make a right. If the child can't be implanted in a woman's womb, it is indeed better to leave them in stasis. It is not right to kill other humans "who will die, anyway" for the benefit of others, otherwise we're back to the Chinese prisoner example.
No one "owns" any human being. Parents do not "own" their children. The scientists that run the labs certainly can not be said to own human beings. For the probable outcome of that sort of thinking, read Huxley, Heinlein, Assimov, Bujold or Herbert,some excellent "future history" or science fiction writers. Or, simply look at the history of slavery.
No one can donate a human life for the purpose of experiments that do not benefit them and certainly not for the express purpose of an experiment that will kill them by design.
No human has the right to kill another to make the life of the first better. The only justification for killing is in cases where the one who is killed is causing an imminent danger to another human life. Self defense does not include killing another human unless that human is infringing on your right to life - is acting to kill you. Even then, the ethical thing to do is to use as little force as necessary to prevent the killing.