Apart from the basic objections one must have to therapeutic cloning, which derives from the sanctity of human life from the moment of conception, there's a further problem when the clones are NOT destroyed. We are mostly conscious now of the situation arising from embryos cloned and destroyed to harvest embryonic stem cells. It would mean creating human beings for the sole purpose of sacrificing their lives for the sake of research. It would mean putting billions of $$ into research that happens to promise very little, and the evidence suggests that it is totally futile: zero successful treatments so far, which is in stark contract with adult and cord blood stem cell research having already resulted in 72 successful human treatments.
No, there's more to it than that. We proclaim that human embryonic life is precious human life, and that includes cloned embryos. Regardless of their origins, cloned embryos are human embryos, even if they were derived from non-human oocytes. What? Note that I'm talking about cloned embryos that are 99% human, which appears to be the case with clones derived from human and non-human oocytes. Why? Because they've removed the DNA from the non-human oocytes and put human DNA in it instead. The result? Not a 100% human being but a being with 100% human DNA. Sounds very human.
Now since we claim that all human embryos are precious human beings, then so are these chimeras. We protest at cloning that creates embryos with the one aim of creating organ raw material (and they are destroyed in the process). Once those embryos are created, we must protest at their destruction. Assuming that scientists capitulate, what do we do with the chimeras? Implant them into surrogate wombs? I suppose that is the logical conclusion, and then we give birth to living, breathing chimeras. How horrible! many would say. But I can't see any other way through this dilemma. Once they're created, it would be murder to destroy them. And that might just be the trap that enemies of life might lay for defenders of human life. They would expect many of us to compromise in this situation and prefer to destroy the chimeras, because, you know, they're not natural. But what would God expect us to do? Here is a new class of the most marginalized, the least of our brethren.
I'm reminded of the story of creation in David Eddings' Belgariad. The children of Ul go to their father-God, asking, I seem to remember, to destroy the creatures that they reject because of their unseemly appearances. And Ul tells them to grow up, and take responsibility. Once made, they must not and cannot be unmade. The young gods are stubborn, and drive the unseemly beings from their midst. In the end, of course, Ul, in compassion, eventually adopts these unseemly beings as his children and subjects.
There are sadly too many Catholics and Christians who consented to the rationalization for therapeutic cloning, and perhaps even clones involving non-human oocytes. They do not realize that, once made, they become a responsibility of all of humankind. Their creation occurs, and cannot be erased in history. Centuries from now, a more enlightened and civilized society will study our history and shake their heads in bewilderment at the wanton irresponsibility of our sadly unenlightened generation. It is a generation where anything goes, perception trumps truth, and subjective goals matter more than objective sensibilities.
Of course, this could be no more than paranoia. Perhaps chimeras can never be created. Evidence suggests, however, that they can create these cloned embryos, only that they will have to go through hundreds of embryos before they can find one to live long enough to harvest embryonic stem cells from. The death toll will be catastrophic and the fury of heaven and our descendants will be more than we can bear. And so the so-called enlightened among us prefer to close their eyes, stop up their ears, and refuse to see, and to hear.