Like I moth, I find myself drawn to the flame.
Could there be a religious/spiritual component to some d/s or non-monogamy situations? If it's an overly hierarchial and authoritarian one, then sure, it could be non-monogamy in a cult-like set-up.
Also, consent was briefly mentioned. Whenever we discuss a complex legal category like consent (even informed consent), we need to make distinctions. To my knowledge, there are at least three kinds of consent, that can be in force simultaneously but also of only one can apply, with sometimes disastrous consequences.
1) a priori (before the fact) consent
You ask me to go to the amusement park on Sat. I think it's a fab idea. At this point, I might have a very hazy idea of what kind of park we are talking about. Even if you show me the website of the park, and I think it still looks great, I might not have sufficient information to make an informed decision about going to the park. What if it's raining and none of the rollercoasters are in working order? Can I get my money back in such a situation? What if the park has a really nasty smell? What if you disappear right after we get in and leave me alone to queue for popcorn?
2) in situ (in action/in the situation) consent
We go to the park, and it's exactly as fab as I imagined it! Thinks could still turn sour. It could start raining, you could still disappear. I might get dizzy after a turn in the rollercoaster and throw up. Someone could steal my purse. Ideally, I would be able to leave in such a situation whenever I want to, i.e. revoke my consent. But what if I lost my purse and have no money to go home? Should the park reimburse my ticket if I feel ill in the middle of my day?
3) a posteori (after the fact) consent
Next day I wake up and still feel the park was fab, and you are fab too! But what if I wake up and realize the day sucked ass? That you were a super-jerk from hell with leaving me alone in the popcorn queue, even though it felt okay at the time. Or that the entrance fee was a rip-off compared with the rollercoasters and LOOOONG popcorn queues.
Of course, in the civil/criminal justice system much more complicated and harmful situations, the risks and responsibilities involved and possible renumerations after things go wrong need to be considered. The same with non-monogamy/alt lifestyle situations, especially when they involve children or partners with considerable power differentials.
Bottom line: we can't just walk past an abusive situation and say "No one's forced to stay, they are adults, nothing we can do", nor can we force people to leave situations against their will even if considerable harm is being inflected on them.
Me: bi female in my twenties