To use or not to use stem cells for research?

Here's the fundamental question I have with using embryos from in vitro fertilization procedures to advance stem cell research: what is the fate of the embryos if they're not used for research?

Are they given to other couples? Unlikely. Are they used for anything else? Probably not. As a result, this means that most of the embryos are kept on storage indefinitely, or thrown away. In either case, that's either destroying a living being, or denying it the right to do anything.

Now, if people are quick to accord a days-old embryo the rights of a full-grown person, why is there no outrage at throwing away these fertilized embryos? And, if they're just going to be discarded anyway, why not give them the chance to be useful in medical research?

I've yet to see a coherent argument from the "pro-life" camp as to why this should be a major problem.