Good vs Evil

            Real people don't think that they are evil. People do what they think is good. Because of this, it's easy to think that people who think differently than you are bad or even evil. Don't fall into this trap- especially when writing villains and even heroes. Don't make either character all bad or all good. Give villains a good goal (that they go about the wrong way trying to reach) or a corruption backstory. In a pro-life story, the villain will most likely represent the abortion mindset. Think about pro-choice arguments.

            The overpopulation argument could easily translate into a villain that is killing a group of people (children or the poor perhaps) to prevent overpopulation. All life needs to be protected, so don't limit yourself to unborn children when another group of people works better for your story. You can use symbolism to relate any group of people to the unborn. Ex: put them in a dimly-lit safe house next to a river to symbolize a womb. Here's where you can get really creative!  

            This is an awesome article (not by me) for understanding how someone could be pro-choice, especially if you have never been.

            For heroes, make sure you don't make them perfect. Let them struggle with selfishness, or maybe even make them sympathize with the villain. (Here is where giving the villain some "good" comes nicely into play!) For our villain that is afraid of overpopulation, maybe the hero grew up in a house with a lot of kids and not enough beds and food to go around. The hero knows that killing people to prevent overpopulation is wrong- but he isn't as convicted as he would like to be. (Give him a character arc- make him change through the course of the story.)