In time, it’s going to be impossible to deny that abortion is violence against children. Future generations, as they look back, are not necessarily going to go easy on ours. Our bland acceptance of abortion is not going to look like an understandable goof. In fact, the kind of hatred that people now level at Nazis and slave-owners may well fall upon our era. Future generations can accurately say, “It’s not like they didn’t know.” They can say, “After all, they had sonograms.” They may consider this bloodshed to be a form of genocide. They might judge our generation to be monsters.
The most common objection is that Thomson's violinist argument can justify abortion only in cases of rape . In the violinist scenario, the woman was kidnapped: she did not consent to having the violinist plugged in and she did nothing to cause the violinist to be plugged in, just as a woman who is pregnant due to rape did nothing to cause her pregnancy. But in typical cases of abortion, the pregnant woman had intercourse voluntarily, and thus has either tacitly consented to allow the fetus to use her body (the tacit consent objection),  or else has a duty to sustain the fetus because the woman herself caused the fetus to stand in need of her body (the responsibility objection).  Other common objections turn on the claim that the fetus is the pregnant woman's child , whereas the violinist is a stranger (the stranger versus offspring objection),  or that abortion directly and intentionally kills the fetus, whereas unplugging the violinist merely lets him die of natural causes (the killing versus letting die objection).