Married monogamous, heterosexual sex has been the favored relationship in law - and for a good reason - it is heathful for individuals and for society. Adulterous, and/or deviate sex is not, that is why society has constructed social and legal sanctions against it. Just as society has constructed sanctions against theft, deception, and aggression between individuals.
Sadly, the wisdom of previous generations is lost on the "whatever makes you feel good" generation.
I think we'll see nature begin to take it's course (or God) ---with the number of STD's and also AIDS being spread, with us moving into the post-antibiotic age, lifespans and reproductivity will soon start dropping. They're saying chlamydia infections are an epidemic in this area ---in the high schools and the girls are losing their fertility at a very young age.