The joke is on them because both of these topics actually implicate complex moral and social questions to a greater extent than "science"
Next time a conservative brings up abortion, ask them if taking a life is ever justified
If they stumble, be ready with the following handy examples: (1) self-defense; (2) war; (3) capital punishment; (4) legally justified police homicides; (5) euthanasia.
So, even assuming you can conclusively establish through "science" that a fetus is a person, it doesn't resolve the issue of what rights the woman has with respect to her womb.