First is due to the Bible. .
Based on the guilt of false teachings that have no biblical basis.
Marriage was about ownership, not sex. A man could have as many wives and concubines as he wished and he owned his women and children. Adultery was only wrong if the woman was owned by a husband. Nothing wrong with single common prostitution only the goddess worshiping temple prostitutes - idolatry was the sin, not sex.
The only exception to one man and one woman was for the elders of Timothy or Titus. We do not know the reason or what was going on in these two Church's.
If a boy doesn't relieve himself he will often have wet dreams as natures way of expelling semen. I was a very conservative in my youth and wet dreams and initial intercourse I put off for many years was painful due to blocked prostate from abusing my body by not masturbation or sex at a young age as in biblical times.
There was never anything wrong with pre-sex marriage as long as the bride price has been paid to the girls' owner (father). Often after price was paid had to wait till age 12/13 to marry but sex was no issue as long as the price had been paid.
On gay men - it would be just as unnatural for them to have sex with a woman, that would be just as unnatural than a heterosexual to have sex with a man. They have just the same natural desires as we do with women. The unnatural act was when armies defeated the enemy in battle heterosexuals would have sex with the male enemies to degrade them that was the unnatural act.
I deal in depth will all these issues at
www.libchrist.com but haven't done any updates for years. Hosted a Christians swingers group for many years and speaker "Swinging Christians not a Biblical Conflict" at Lifestyles conventions. As long as done with the consent of partner nothing biblically wrong since not stealing one of the wives of a husband if gives permission.
We were featured on the front page with a humorous article "what are you doing on Sunday Morning' and long article. We had about 100 single men contact us but we were strictly a couples group. How to help single men was how I got interested in sexwork and the rest is history. Have been active on Fred Z's (RIP) original board before it was the "erbs". First explored Montreal, than Victoria and for the last 15+ years Toronto where I have about 2500 posts on terb. Avoiding of course the legal issues in the US.