The argument doesn’t understand what the moral uncertainty is over; it’s taking moral uncertainty over whether fetuses are people in the standard quasi-deontological framework and trying to translate it into a total utilitarian framework, which winds up with fairly silly math (what could the 70% possibly refer to? Not to the value of the future person’s life years- nobody disputes that once a person is alive, their life has normal, 100% value.)
The argument doesn’t understand what the moral uncertainty is over; it’s taking moral uncertainty over whether fetuses are people in the standard quasi-deontological framework and trying to translate it into a total utilitarian framework, which winds up with fairly silly math (what could the 70% possibly refer to? Not to the value of the future person’s life years- nobody disputes that once a person is alive, their life has normal, 100% value.)