Why is everybody so concerned that young adults might be damaged by sex? Most people enjoy sex. How about say... circumcision (MALE and female) -- the unnecessary surgical removal of a majority of the nerve endings in the genitals? 100% of infants are unable to give informed consent and 0% of parents have the right to mutilate their children. 0% of circumcision patients enjoy it and all of the practice is, by all definition, worthy of nothing less than complete moral outrage. That's been known to cause a hell of a lot of psychological trauma for those who figure out what's been taken from them.
For you circumcised men out there, there's a reason that dark ring (the scar) is the most sensitive part. That is all that remains of about 20,000 nerve endings that were hacked off of what is, most likely, your favorite part of your body. Additionally, the tip is dried out and less sensitive because what should be an internal organ (a mucosal body, not entirely unlike the inside of your nose) has been made external and allowed to weather and chafe.