By permitting abortion -- the killing of human beings before they are born -- we discriminate on the basis of age, size, stage of development and condition of dependency.
This discrimination enables further discrimination based on disability and gender. More than 90 percent of unborn human beings diagnosed with Down syndrome are killed for that reason. Babies with many other disabilities and "imperfections" are also aborted. Abortion for sex-selection (aborting a female baby because her parents want a boy) is widely practiced in China and India. And it also happens (to a much lesser extent) in the United States.
Such discrimination would be considered noxious and indefensible in any other context. Only because the unborn have already been discriminated against (excluding them from the human community of those who are owed respect and protection) may they be further discriminated against on the basis of characteristics widely recognized as morally trivial.
Discrimination on top of discrimination.