Sex is only controversial because it is intellectually ignored as a basic human instinct, during a human early development. Due to choices of avoidance.
I imagine early humans did not avoid the subject, as there is no sound "reason" for doing so. Yet somewhere in social evolution, concepts and groups made decisions about what was acceptable to be spoken about, taught and reflected upon.
Only things that are not equally and/or properly understood are controversial. For lacking equal and proper understanding.
Any human being would benefit from being appropriately taught that one aspect of their humanness is their sexuality from the first day of their curiosity and desire to learn. Which would be very early on and beneficial because it would seem less odd or taboo as they mature and their ability to make sound, safe, and self-less decisions would increase exponentially.
Connecting-to-the-Value-of-Why 2005-2008 ©