“These studies indicate that adult stem cells show far more promise than embryonic cells to treat diseases.”
This isn’t true. There has been far more research done on multipotent stem cells, so there are more current therapies, and more that will probably be useable in the near future. The use of pluripotent cells is more complicated, and there are some difficult challenges faced. That doesn’t mean that there isn’t promise or potential in the treatments, only that their use is further off in the future.
Ending a human life for the "further off" hope that it might do some good some day, when there is all kinds of potential and success without ending that life MAKES NO SENSE.