you nailed it (no pun intended).
Even in areas where they don't get specific, the overall obsession with SEX=BAD screws your mind up, it sexually stunts people from a regular course of discovery and self knowledge. So you get people who lived unfulfilled (prudish) sex lives, and you have people who crack and go off the deep end.
The WTBTS has convinced that anything other than what you described WILL lead to the following:
- Irreparable heartbreak and guilt that will last your entire life
- Sexually transmitted disease
- Unwanted pregnancy
All those things are implied guaranteed by the "society" if you don't follow the sex rules