In order for this to work, you'd probably have to do away with the idea of a single child birth. You'd have to work with litters, anywhere from 5 to 9 children each birth. I don't think the math will work any other way.

The question also comes up in how often people are dying. If you assume that even in a sociopathic world that doesn't care about the murders of other people, you would still essentially have to have murder as a fetish be a fairly abnormal sexual desire. It's not so much that you have a case where every now and then a person gets killed by someone with a fetish, but the simple fact that if it's socially permissible it's going to happen far more frequently.

Given the permanent nature of the act, I can't help but imagine that you could easily see high sexual value men with a penchant for slaughter ending up with over a thousand personal kills. Think of someone like Bill Clinton and what he would have gotten away with if he liked killing girls and girls liked getting killed. How many thousands would he have gone through? Ten? Twenty? An addict will get high as often as possible and if you can just stick a knife in people that's gonna be something you do a LOT.

It's also possible for a more 'mature' society to just accept it as a part of life. What if there were no sex addicts that like hanging girls and people just responsibly only murdered long term girlfriends or wives? Such a thing could happen, maybe it's simply barbaric to indulge such wild fantasies. Sure, you can go to the store and just spit a fellow shopper, but it's so unfashionable that people just don't do it.

You'd still end up with a lot of 12 year old boys running around with their cocks out and a .45, but we were all young once, right? Perhaps wanton murder sprees are only the stuff of unregulated youths, but they'd still take a toll on the population numbers. Kids like experimenting, especially when it involves sex.

"Sure, I tired murder when I was in college, who doesn't? But after a while I just stopped enjoying the feel of a used, cold vagina. I much prefer the warm ones. And besides, do you know how frustrating it is to have to keep training your girl how you like having your knob sucked? I swear, over the course of a week I must have strangled the life out of at least 3 girls who just wouldn't listen when I told them 'more tongue.' Wild times."

There's also the ramifications of future losses. Sure, you've just murder raped your sister in her bed, but she was only 8 years old and now you have the problem of all the children she wont have further down the line because you got horny one night. It happens, we've all been there. Still gonna be an issue, though.

You also need to consider general frustrations as well. Let's say you're in traffic and you notice the woman in the car in front of you is putting on her make up when the light turns green. In reality, you lay on the horn to get the bitch moving. In a world where murder is acceptable, you pull out the .22 and see how many shots it takes before she stops squealing. It might not get you to your destination faster, but it sure is satisfying.

I dunno. It's possible that our inherent desire for self-preservation and the preservation of those around us might just be the reason we as a species(in fact, every species) is still around. Shame, really.