the christian rules about sex? why? , page-120

The problem with rape and causing suffering in others is it is sin. The ancient middle east where several religions originated favoured stoning as a means of execution, rather a cruel way to go I would imagine. Killing some one even a sinner was sin and by every one contributing stones the guilt could be shared.
I would be very surprised if atheists as a group are less likely as any other to commit sex crimes. Christians rape because they are sinners. Weapons/guns are tools, they are useful for hunting, even in farming they have uses. Christians as a group include all types of individual, some with bad attributes; sinners, fools, aggressives, etc... However some times there is a need to defend oneself and family, communities and country from evil.
If you dont want to protect yourself against the wickedness of others least you cause suffering you are very noble indeed. To me it would be a sin.