You may have missed where I mentioned that I wasn't much of a historian, and that I don't know the reasons behind the prohibition. You may have also missed that I wasn't trying to call you out on your historical knowledge or ability to tie in past and current events, but was stating that private vices and public vices are perceived in different ways and are thus handled differently. For your example, being drunk can be considered a vice on both the individual and public scale, but being drunk in public is considered far worse of a situation, and thus a much greater "vice", than being drunk at home or in a private establishment, where it's been established that it's more acceptable (note that it doesn't mean it's completely acceptable, just more acceptable than being drunk in public), thus less of a "vice".
To tie it back into the argument here, sexual belligerence is considered a "vice", and even that standard is sketchy at best (considering the massive double standard in the American public in relation to male and female sexual belligerence); in this case, sexual belligerence by the spiritual and moral leaders of a given community. My simple, malinformed point, is that neither of these are important, as the problem seems to be that children are being victimized in a system where trust is implied with authority given.
Well, they didn't realise that sperm was constantly broken down and reformed, obviously. So they probably thought that by ejaculating anywhere other than a woman, where it had the chance to develop, was 'wasting' it.
At least, that's my understanding. I am no expert, though, and I cannot cite where I read this.
Be not afraid...Umm... that is not in the Bible.
Do you highlight everything looking for secret messages?More than that — since they didn't know much about the female internal bits, the semen was basically all they saw of the process until a baby popped out. They may well have thought the semen was the sum total of how babby is formed and spilling it in vain would have been killing it.

Any ideas on how to effectively neuter the anti-vice movement?
You exist because we allow it and you will end because we demand it.