It occurred to me that in Aldous Huxley's 
Brave New World,  there is the concept that "everyone belongs to everyone," which is just a  euphematic way of describing socially encouraged sexual promiscuity. (I  don't judge.) However, the promiscuity is limited in the society Huxley  created by male-female couplings. Women are expected to have fleeting  relationships with as many men as they wish, and men with many women  (though not at the same time). There is no discussion of promiscuity  outside the bounds of male-female relationships.
Granted, 
Brave New World  was written in the early '30s, so the idea of promiscuity in general  was probably less scandalous than the idea of homosexuality or any  non-M/F-sexuality (However, I cannot be sure, I'm not from the '30s).  That though, the different degrees of scandalousness, is absolutely  fascinating. The idea that one idea is taboo, but another is double  taboo. Like, for example, swear words that have different levels of  gasps attached to them if used in front of parents, or certain  audiences. A child says shit-(aki mushrooms) and parents' eyes get wide  and they direct the youth toward the preferable "shoot,"-- but a child  drops an F bomb and parental units tweak as if miniature grenades just  burned the soles of their shoes, and proceed to take away privileges as  if they were candy. Why is there that distinction?
It  makes sense though, due to the cliche which discusses the many shades of  gray in life. It's the difference between belching and mooning someone  at a black tie event. Society is just wonky. 
Belated disclaimer: I have not read 
Brave New World in a year, as it was summer reading for AP English, so my recollections are probably hazy.