The biggest source of embryos for research right now is not abortions, as some seem to believe, but the in-vitro fertilization industry. It is not unusual for a couple to have many more embryos than they could possibly use created, only to be left in storage indefinitely or destroyed (or used for research) when that couple has completed their family.
There's an argument to be made that using "leftover" embryos for research is more compassionate than simply destroying them, which is the other most-likely option for couples who don't want any more children, and don't want unknown genetic full-siblings of their children out there either.
Perhaps the United States should enact regulations such as those in Britain that limit the number of embryos a couple can have created at one time.
The wrongness of creating human beings that will be discarded doesn't justify the wrongness of using those human beings for research.
Embryonic stem cell research is wrong.