The Church views the intentional wasting of semen (Onanism) as a mortal sin. The question is not intended to be offensive, but thought provoking.
Consider the fact that the church even forbids this practice when another pregnancy would place the wife’s life in danger.
Also, people need to stop buying into this stupid notion that rape is purely about violence and domination and has nothing to do with sex.
The primary reason rape occurs is the out of control sex drive of the perpetrator. The difference is that the rapist is by nature a jerk who will resort to violence to get sex and has absolutely no regard for his victim.
Here is where problems occur in the difference between Biblical/Christian morality and the human moral sense - the notion that certain moral instincts about interacting effectively with fellows have developed throughout the millennia over which human beings have spent living in social groups.
The Bible, in particular the Old Testament, is rather sketchy on the subject of rape, as has been demonstrated in previous posts to this thread. As far as I can recall, the New Testament does not mention rape in any particular way (though feel free to correct me here). Thus, Biblical morality falls short on this issue.
Christian morality, if taken from an historical viewpoint, has had little time for the issue of rape. Historically, once a woman was married, her duty was to submit to her husband, in whatever form that took - otherwise she risked social ostracism at best, and violence and possibly even death at worst. Marital rape has only been recognised as a possibility, let alone a crime, within the last 100 years.
We are therefore left with the intuitive, evolving moral sense that humans, in general, possess - if it has not been subjugated to indoctrination in one form or another. Most thinking people would agree that forcing a person into sexual intimacy against their will is wrong. It is a violation of
personal autonomy, a notion which is almost universally accepted amongst humanists (if you’re looking for any group other than Christians/theists that claim an interest in defining morality). In this instance - taking into account the total harm caused to the victim - there would perhaps be some ethical mitigation in the rapist’s voluntary withdrawal before pregnancy could occur. However, given the uncertainty involved, that mitigation would be absolutely minimal (if present at all), given the nature of the act of rape, in and of itself.
To suppose that rape is about sex - or a disordered sex drive - is also a misrepresentation of the issue, I believe. To force intimacy upon a person without their consent is a gross violation of their free will, and I think that is the key to understanding rape as a crime, and a sin, if you will have it so. This crime is certainly compounded by attitudes towards relations between men and women; if you are brought up to believe, or if you somehow come to believe, that it is a man’s right to have sexual relations with a woman, then the woman’s free will falls by the wayside - the man’s power and the man’s will become paramount in such an interaction. (Please note that I am here only dealing with heterosexual rape - homosexual rape, while still a gross violation of free will and free association, is a qualitatively different issue, due to the attitudes of mind involved).
Thus, while I am suspicious of the intentions of the original poster, I still think this is a moral issue worth discussing.
now I have “that” song stuck in my head! 
