In our society, there is probably no single issue that causes as much division and controversy as abortion. Although there are plenty of good people on both sides of the issue, it is imperative that both sides give good, compelling arguments that stem from facts and reason as opposed to emotion. Pro-lifers lose the argument every time they cite their religious beliefs, the Bible, or other religious texts, because not everyone shares your personal religious beliefs, and we don't decide public policy based on religion. However, despite the occasional bad arguments that abortion foes make, it is almost always the pro-choice side that gives the weakest arguments that stem primarily from emotion or a lack of philosophical insight. If you're pro-choice, please avoid making the following weak arguments and research better ones.
1. "My body, my choice."
I've lost track of how many times I've heard this argument, as it arguably serves as the bedrock of the pro-choice viewpoint. Because the fetus resides within the woman's body, pro-choicers argue, she should not be forced to carry it to term. First, let me say that, sadly, I have encountered some people who go so far as to say that the fetus actually is a part of the woman's body. I could be rude and ask them if they slept through their high school biology class, but I always try to be civil and state that the fetus, because it inherits half of its DNA from its father (and often has its own blood type as well), cannot possibly be a part of the woman's body. The science is clear that it is its own organism from conception.
However, I think most of the time pro-choicers argue that the woman has the right to an abortion merely due to the fetus' location inside of her body. Even so, this argument can fall apart quickly if you know how to counter it. First of all, if the woman has the right to kill the fetus because of its location, does she also, then, have the right to torture or mutilate it in any way? Let's say that she's a deranged sociopath and wants to hire an abortionist to use a pair of forceps to remove an arm or a leg from the fetus. Should that be permitted?
Secondly, consider this analogy: Let's say that you're on a cross-country flight from New York to Los Angeles on your very wealthy parents' private jet. Midway through the flight, your mother decides suddenly, for whatever reason, that she no longer wants you on the flight, and she wants to throw you off the plane immediately. Does she have the right to do this? After all, it is her private jet and her private property. Most people would scoff at the idea that she should be allowed to do this because your right to life supersedes her right to have complete dominion over her property. Similarly, the fetus' right to life in this scenario supersedes its mother's right to have control over everything within her body.
2. "Religion doesn't decide public policy."
Fortunately, the above statement is true. I don't want to live in a theocracy because I believe that religion (and the virtuous behavior that can stem from it) should be voluntary and left up to the individual. However, we do make legislation based on Natural Rights, such as life, liberty, and property. Whenever one of these rights is infringed upon, the state can and should intervene. You don't have to be a religious person to believe in the idea that every human has certain rights that deserve legal protection. I'm pretty sure that most atheists believe that violent crimes such as murder should be prohibited. And, whether you agree or not, there are tens of millions of people in this country who believe that a fetus is a person from the moment of conception, and I would say that the onus is on you to establish a philosophical argument that demonstrates otherwise. Thus, if you believe in the concept of fetal personhood, as many atheists even do, you don't have to be religious to oppose abortion. This shouldn't be so complex, and yet somehow it is perceived to be that way.
3. "You just hate women."
First of all, shame on you if you've ever resorted to this argument. This is by far the most egregious and offensive of all the arguments that I've ever heard in favor of abortion, and I think it's also the least logical. I am against abortion because I believe it to be murder. No, feminists, there no "patriarchal conspiracy" designed to systematically oppress women. You all do that on your own by viciously mocking housewives and stay-at-home moms.
Secondly, pro-lifers do infinitely more to help women through unplanned pregnancies (and beyond) than pro-choicers do. You say that you want to abortions to reduce the number of abortions, and yet you do nothing to give women other options. When pro-choicers start opening up crisis pregnancy centers en masse, let me know, because it seems that pro-lifers are the only ones who do that. I am of the belief that no woman really wants to have an abortion, and that alone speaks volumes. We need to show women that they have help and other options available, and ironically, it seems that only pro-lifers understand this concept.