Some argue that the potential benefits from medical research using embryonic stem cells are outweighed by the possible life that could come from the embryo. It is important to note that embryonic stem cells are usually discarded unless they are used for research purposes. Others say that using the cells help the living and help further advances in medicine and could save lives.
It is a very emotional subject and people generally have a strong belief for one side or the other. The American government has made several rulings against and then for this testing so it is important to keep up with the most recent laws.