TL;DR Unprecedented availability of multiple vectors that enable promiscuity today, unprecedented self-reinforcing feedback loops that strengthen specific models of behavior.
We haven't seen anything yet, this is just the beginning.

> People have been having sex with more than one person for a LOT longer than the 80s.

This is not accurate for less-developed countries, which is what I mentioned. I've lived in eastern Europe during the 70s and the 80s, the social stigma for a woman having multiple sex partners before marrying was enormous. Doesn't mean it didn't happen but it was definitely not the norm. Today, teenage girls in the west go through sexual partners like they go through cell phones.

> What you are framing as a crisis caused by too much female sexual choice is in fact a crisis of inequality wherein females are choosing "not poor" and the group "poor" expands year after year.

Income inequality is a very weak factor and does not explain female hypergamy today. Spend two weeks living on campus in any US college watching poor but extremely attractive male students and you can validate that for yourself. Money does not buy love or sexual attraction. Spend some time on incel forums reading their posts, assuming you can see past the hate and lingo, and you will realize that most/all of them crave these lost-youth experiences. They don't necessarily just want a partner in their 30s or 40s, but to feel wanted and loved in their 20s. Once they realize that opportunity is gone forever, they have to pick up the pieces.

> Incels are a group not of those who aren't getting any but rather those who aren't getting any who have decided to blame society in general and more particularly women.

This is very superficial since you are not examining the root causes. Look at advertisements today, movies, sports, Facebook, Instagram, reality shows, series on Netflix. We are bombarded by models of sexual attraction every minute of every day, models that are so skewed towards a specific minority that your average physically unattractive male literally stands no chance whatsoever. It's these projected models that strongly reinforce female hypergamy (for both attractive and unattractive women) while at the same time pushing the unwanted males further into the abyss. The worst of all possible worlds. Additionally, not only have all artificial limiters (e.g. social stigmas and pressure towards non-promiscuity) been lifted but accelerators like Tinder have wreaked havoc. Carnage on a societal level.

> If you want to decrease the negative impact of this behavior address inequality, make mental health more broadly available at zero cost, keep shutting down such communities and start putting people in prison who publicly call for acts of violence against others.

If you take the OkCupid studies seriously (you should), then you'll realize how antithetical to any sort of progress your recommendations are. You can't hide this problem or explain it away by shouting mental illness. This is a huge chunk of the population at large and if you miss or deliberately ignore the root causes because they tend to make you uncomfortable then your approximation of reality is completely off and any sort of analysis that you're performing invalid. Look at smoking in its heyday. Imagine being blasted by "smoking is cool" ads, watching most of "successful" society smoke whilst you not being able to afford even a single cigarette. How would that make you feel? Is that a mental illness on your part? Is it not conditioning massively amplified by very specific agents and societal effects? Should you just learn to "deal with it?"

Now consider that smoking is neutral in terms of self-perception of how other people see you compared to sexual rejection by other living, breathing humans. The psychological damage of realizing one is not wanted can be immense. We are talking about a core biological need and for the vast majority of people reason to exist. Surrogate activities (video games, traveling, hobbies of all sorts) are the counterbalance but they're not yet good enough to make this problem disappear.

OkCupid research opened the floodgates but there will be additional studies like the one linked here and societal effects coming home to roost (as it's been clearly happening). At some point, those effects will be too obvious to be ignored or explained away. Let us hope that ways to manage this catastrophic problem manifest, before the ticking time bomb goes off.