Weimerica is a pretty weird place. Even the liberals who write "Family Guy" have caught on as after some latest gay event they had a character touch his son, and when his son stopped him, the father said, "I don't know what's right anymore". How do things catch on though? How does S&M move from the dungeons, unspoken parlors and clubs to commonplace discussion amongst friends? Deviancy makes its way from the top of the status chain down with the help of the media.
Any person's status is made up of a basket of items: wealth, looks, job, education level, home, geographic location, religious affiliation, etc. A sexually deviant behavior is by definition a behavior that is not normal. It deviates from the norm. Being abnormal, especially in the bedroom would be a hit to one's status. In order to secure your spot in the status range of your desired class, you better have great measures for all other status inputs. To be openly deviant, one must have a great status aggregate to sustain the status hit by coming out as gay, trans*, an S&M enthusiast, etc.
This plays into the media's wheelhouse as when needed, it can discuss a high status person, remark that they are gay/trans/poly and then declare that this is okay. It must be okay because the media would not risk scolding the wealthy or high status. For example, Elton John coming out in the late '80s was not going to get a tsk-tsking despite HIV/AIDS raging all around the gay community because the media still needed him to sell records. Any deviant behavior can be treated the same (think Bruce Jenner and trans*), and the high status first adopter is required. The high status person then can serve as a symbol for others to emulate, and for the behavior to translate down, a person must have enough status for lower status people to want to emulate. The New York Times did this with 50 Shades of Grey several years ago. Note that big city metro houswives couldn't get enough of it, ahem, higher status ladies love it, so you should too. Universities help spread the acceptance, and if one looks at opinion polls, college educated voters support gay issues far more than those who avoided college. The college educated set supports it, the media will blast, and college credentialed citizens are high status.
One pretty good example of this top down sexual deviancy drift is lesbianism or female sapphic experimentation. The elite might have had a lesbian or two in their network, especially if they had Jewish friends, decades ago. MTV and good old Madonna helped it out in the early '90s, but it was still weird. Madonna went too far then, but do not dismiss the power of the Real World having a cute lesbian or bisexual girl on every other year. Even if you went off to college in the '90s, you heard of LUGs or BUGs. Those lesbians until graduation types though were going to private colleges (Sarah Lawrence, Haverford, Middlebury, etc) and from higher socioeconomic homes for anyone in their family to discuss it. Your prole friends would look at those girls as lame or weird, especially the prole girls. Angelina Jolie talking about being bisexual helped it along, but eventually, the same sex experimentation found its way down market. Now if you have a female relative go off to college the default assumption is that she'd hook up once with a girl or even have a short fling with a woman.
In contrast to this, you can destroy or stop something by associating it with low status people. This is the progressive media method. If the reality of gays and their behavior were shown, no one would support it, but alas, it is not. Going on offense aganst the poly push, one could set up a secular sounding institute, "Civilization Research and Security". This institute could spend some cash and commission some surveys of people about their views of poly behavior and even try to get a decent sample of poly people (might be a good thing to seek out). Due to the mass ignorance about percentages, weight and whatnot, you could present poly people as overweight, middle to lower earners, smokers (of what we would not say) and anything that in our current culture is considered low status. Associate poly with low status, note that no brownie points will be earned by supporting such uncouth individuals, and you will not get the big swing to supporting poly acceptance. "Who wants to support those losers" is what the single women will think.
Over time, the status ding evaporates, allowing lower status people to openly flaunt a deviancy without the fear of sliding down the status ladder. Someone higher status must exhibit the behavior in order for them to claim that X does it too, so why can't I? Some movements are ground up, and other movements are top down. America is a supposedly classless society yet it still does have classes, and no one wants to fall down the totem pole. Humans are a social animal, and few want to be the prime mover and risk the diminished rank in the herd. If you want to know where deviancy is heading, do not look to the masses, look at the Lifestyle section of the New York Times and the "Science of Us" in New York Magazine.