[Embryonic Stem Cell] lines come from material stored at fertility clinics which is already slated for destruction. Preventing these blastocysts from being used for research won't 'save' them. It simply means they'll be disposed of in a medical waste facility instead of being used to find cures for disease. The only reason to restrict federal approval of new lines is to appeal to a minority of extremist social conservatives and it comes at the cost of possibly delaying or denying treatment--and in some cases life itself--to millions of people.The bill has already passed overwhelmingly in the Senate, but not quite enough to override a veto.
The president argues that taking stem cells from an embryo that is likely to be discarded anyway constitutes murder. There is, of course, no law that would punish someone for murder for discarding an embryo, but The Decider has never been a stickler for the law.