"The rationale given for using aborted children’s bodies in medical research is usually that since the children are going to be killed anyway, some good might as well be had from their remains which would otherwise be discarded."
But let's fast forward a bit with that "logic" and apply some simple economics to it. Any commodity that has a demand will soon have a supply arise to meet it. Be it gasoline, food, shelter, clothing, chemicals, illicit drugs, or what have you. Once you allow the demand to develop, the supply will develop as well.
Do we really want to see a market in aborted fetuses? Because that's where this is going. The frightening part is that a significant portion of the populace appears willing to allow it.
I'm hoping the research on placental and adult stem cells pans out in lab and clinical trials as more viable than embryonic stem cells. Otherwise, the outcome you fear shall be inevitable.