I mostly agree with you on consensual humiliation/sub play, but it can be a slippery slope!
I mentioned it in a discussion in another thread, while my wife and I do not share/swing (beside some bedroom fantasies and roleplay), we have old friends who do. We have been invited and visited several times "parties" of theirs, since several of the boys and girls there really like an audience.
We had some games there (just with each other) and we are sure we were watched at least once, but no problem on that front, did not infringe on our fun.
Due to this we have quite a bit of insight into what goes on and how interestingly variable the likes and dislikes of various couples are. For instance, there is a couple which draws the "not further than" line at cocksucking and pussylicking. Luckily for them she absolutly loves cocksucking (which might be one reason they do not go further). Since they are married he is the only guy having her pussy, but the number of guys she sucked off is - very impressive!
(They are one reason I took the sperm breath example in the earlier post)
But the main point of my rambling is that there are some distinct similarities among the couples who share/swing long time without major problems.
- consensual (cannot be stressed more) sharing/swinging/hotwifing, usually the couples who fare best have broadly similar fantasies and desires
- No is no (esp. if one partner absolutely does not like something) and no "squeezing by" the chosen rules
- have some fixed rules, only be changed if both partners agree
- strict division between bedroom and normal life
As said before, there is a lot of variation what various couples who share/swing/hotwifing like and do. Some are just dipping their toes (so to speak) and stay "vanilla" nearly everywhere and are happy with it, others go really wild amd some mix it up.
We know a couple where you´d never guess from normal life what loose cannons in the bedroom they are! She is a among other things a true slut in bed who loves gangbangs and he loves her that way, but they have some few things which are a total shutdown. Among them "bodily functions play", SM and humiliation stuff, they would never abide with this.
We also know a couple who is among the minority of NTS couples who like humiliation play (from all the couples we know of who share/swing, just 3 are into it), but they for instance would never do some things the wild couple does regularly.
But to get more to the point, humiliation play is a slippery slope as I wrote above, because we could see how one of the 3 couples broke down bit by bit, despite several tries to help.
Their problem was that they did not keep it to the bedroom, it crept into their normal lifes and it broke them. Humiliation stuff can erode respect quite easily and if not kept on a tight leash, it will burn you. There is simply a difference if you treat someone like a doormat or if you wade into the throng of guys banging your beloved slut to take part and make sure she gets to fly even higher, what she knows and loves.