I will avoid comments like "slippery slope," and so on. I am not in favor of embryonic stem cell research. We know that life starts at conception, if it didn't then the cells wouldn't continue to grow. Left to mature, what do you get? A baby!
I believe that honest attempts at using adult stem cells and those of newborns and placental tissue have not been fully explored. People have a tremendous ability to exploit and profit from things that they shouldn't. Embryonic stem cells are "handy." They can be selective about who/what they clone or extract cells from.
We know as nurses that none of us gets out of this world alive...we all die eventually--no matter what we grasp at to try to avoid it. I could not in good faith try to "cure" any of my illnesses if it meant that someone else (no matter how young) was literally created and destroyed for my sake.
We know that science can do a lot of good things--but creating a class of people that we use as we see fit is nothing more than slavery. Which has been outlawed in our nation for a number of years, as well it should be!