An embryo has no conscience, no sentience. And besides this isn't even embryos it's stem cells. They fertilise an egg and start harvesting the genetic factory that comes out of that for stem cells (something like that, right?).
Regardless without any sort of moral law we can remotely apply towards it, it is about as morally wrong as throwing a stone. The reason you may think it matters is because you apply too much meaning to humans -- even their individual cells have the equivalent value as the full human being.
That's not consistent.
