Does the word "contraception" mean anything to you? Maybe if that child is unwanted, precautions should be taken to avoid pregnancy in the first place. There are many methods, some more effective than others.
Also, if "it's legal, therefore it's justified" was a valid argument, then we'd still have race-based human slavery. Try again.
Thirdly, Genocide as a means to cure diseases is a little bit extreme, don't you think Herr Himmler?
Fourthly, Abortion as a means of global population control is a myth. All you're doing is shifting where in the world the majority of the babies are born. The population is still rising.
Finally, Abortion isn't a political issue. And, news flash: It isn't a moral issue either. It's actually a civil rights issue.
Here's the thing about "when does life begin"... It's not a relevant question. Because as long as you keep your salad tongs out of the uterus, chances are high it will eventually cross the threshold of "life", no matter where you arbitrarily put it. And if it's alive and it's human, then it's entitled to civil rights as guaranteed by the Constitution. You cannot rationally justify taking away someone's civil rights because you arbitrarily decided they're not human, and therefore not entitled to any. We fought a civil war over that, and a lot of people died. Here's hoping we don't have to fight another one...