I hardly think that a woman would be so eager to get pregnant again so soon.
Most likely, she won't be eager to have a rapist's child. She might be desperately eager to have her husband's child.
If a woman is (say) mid-thirties and married, and is raped and becomes pregnant, she might very well lose the chance to ever have a child with her husband. Who are you to say whether she should want to have a child with her husband or not? The rapist ends up with his genes perpetuated, the husband does not (and he's left paying the bills).
Innocent people die every day, particularly in war. No one suggests we give up war because of that.
Now - for me personally, I will not use birth control pills or IUDs. Both of these birth control methods run the risk of causing very early abortions. I think you could even argue that tubal ligations have a slight risk of causing abortions (because ectopic pregnancy is more likely). Plus, pregnant women who smoke have a 40% higher rate of miscarriage - lots of lost babies there. To me, all of these methods and activities are immoral, so I don't do them.
Focus on getting women to voluntarily abstain from abortion; you will be much more effective.