Surprisingly, there was an interesting article in the normally indistinct Mother Jones magazine. While the article doesn't criticize embryonic-destructive research, it does recount the manner in which those who participate in the creation of embryos come to view them and, contrary to the spin, a stubborn awful lot of them, don't want to donate the little "cell masses" for research or even to dispose them.
A researcher who has studied the reaction of parents participating in IVF, concluded that "Some saw them as biological material, but most recognized the potential for life ...." The article notes the reactions of many mothers such as one who began with a mechanistic notion of what she was doing, but then noticed that "You start saying to yourself, "Every one of these is potentially a life." Others expressed the desire to use them all or an inability to make any kind of decision. Research of destruction doesn't seem right.
Unless you defeat that innate sense of the sacredness of human life. For that, reductionism is the answer. "Little lives, that's how I thought about them," said one woman. "But you have to switch gears and think, "They are not lives, they are cells. They are science. That's kind of what I had to switch to."
You have to because, if you don't, well, that starts to get inconvenient.
One might call this dehumanizing them, but who wants to be ungenerous?
The invocation of the God "Science" in defense of that is chilling.
It does show how the slippery slope might work. Pull down one barrier and then claim that there is nothing distinguishing the next one.
(NB; The article does point out that the creation of excess embryos is not a necessary feature of IVF. In Germany and Italy, you can't create an embryo unless ou are going to implant it.)