Yeah, ethical non-monogamy is a third rail in most circles, I've found that out the hard way as well. I'll say I've found it somewhat puzzling that tacit non-monogamy (aka, Spinning Plates) is embraced here, but ethical non-monogamy is not, despite being arguably very close on the spectrum.
I'm not 100% sold on the fact that ethical non-monogamy works for both sexes though. There's a strong emotional component for women more so than men and they have a higher chance of falling in love or getting emotions tied up when sleeping with others. That's why I think it can only work for guys mainly. I'm not saying guys can't fall in love with someone if they sleep with them long enough but chances are more rare than women, especially if their significant other is treating them very well. You can see this from history where guys that's slept with women outside of their marriage end up staying married but you can't exactly say the same with women in the same scenario. That's what I expressed to the wife and told her that I prefer her not to go outside of the marriage. So far she agreed not to but is waiting for me to get my $hit together and figure things out or she will leave.
But then there are also scenarios where guys just get tired of having sex with the same person over and over and give up having sex with their partner and that's totally the fault of guys. Those are the cases where you see women going outside of the marriage and the guys basically condone cvcking so they don't have to deal with it and can pass off "their problem".
There are also scenarios where both are naturally swingers and are able to separate out the sex from anything else. They often have very strict rules they abide by as to not get into any trouble.
There's a lot more to this with unique individual situations/dynamics and details but that can turn into a book in itself.