There has been a battle in our government over sex-selection abortions (that is, abortions for no other reason than their gender). There was a measure put forth that would ban sex-selection abortions, but our government voted recently against this measure. 
At first blush, this seems pretty ridiculous to me. However, upon closer examination of the pro-choice position, can you really blame them? When the Roe v. Wade decision was passed, the Supreme Court decided that no one can tell when human life begins (despite blatant scientific evidence to the contrary), then took it upon themselves to declare that life begins at birth and made abortions legal through all nine months of pregnancy.
Now, if the unborn are mere "clumps of cells" or "tissue," and are not "humans" as we are, then why is sex-selection abortion wrong? If a couple is trying to conceive, is the father wrong for hoping he gets a son? As long as he doesn't mistreat or abuse his child if she turns out to be a girl, of course it's not wrong. And if abortion is about the woman deciding whether or not she wants to be pregnant, not about whether or not she wants to remain pregnant (as pro-choice advocates assert), then what's the harm in aborting a child because she's not the gender you want? You're not causing any harm to anything, if the thing you are aborting isn't a human.
Polling data actually suggests that the majority of Americans (in fact, 86%) believe that sex-selection abortions are not only immoral, but should be illegal.  So let's take this a step further. Say a woman gives birth to a girl and when the girl is two, the father decides he doesn't want her and wants to try again (he really wants a boy). Would he be morally justified in taking the child's life because she's female? Of course not! So why do we feel so strongly that sex-selection abortions are horrible? Could it be because the unborn that we are aborting is a human? Why would sex-selection abortions be a human rights violation based on gender, if abortion itself isn't a human rights violation based on race (human)?
Steve Wagner suggests disgust over sex-selection abortions might be for one of at least three reasons: It's sexist, it's a crime against society, or it's a crime against humanity. But none of these reasons work unless the unborn are actually human. If it were merely sexist, then this could be remedied by ensuring that an equal number of male and female fetuses are aborted. Yet no one recommends killing male fetuses to balance the numbers out. It's not a crime against society. Concerns for the beauty and order of society do not really account for our disgust. It is perceived as wrongs not against something but someone. And it can't be a crime against humanity unless the beings being wronged are actual humans. Potential humans cannot be harmed. In order to be a potential something, it is an actual something else. If it is merely a potential human, that would make it actually something less significant, like an animal mass or tissue organism. But it is not a crime against humanity to remove a piece of tissue or kill an animal organism. 
Christopher Kaczor would add, "Discriminating between non-persons, for example plucking the red roses but leaving the white, is not ethically problematic in itself, since these plants do not have rights nor do they merit equal respect as persons."  Sex-selection abortions are simply not morally problematic unless the entities being discriminated against are fully human with the same moral worth we have.
 Wagner, Steve, Common Ground Without Compromise, p. 53.
 Kaczor, Christopher, The Ethics of Abortion, p. 198.