Can you tell this issue, of not acknowledging the line between fantasy and reality in kink, really gets me upset?
I wanted to expand on my comment above that I find it anti-gender-equality to say that a man who's ok with his wife having rough sex with someone else and then coming home to him "is" a cuckold. A cuckold, again, in popular understanding, is a man whose female partner is unfaithful to him and who then humiliates him by rubbing it in his face.
The main thing that hampers gender equality is the idea that there are certain things each gender inherently is or should be. Women are weak, soft, small, submissive. Men are strong, hard, big, dominant. Screw that, we are each what we choose to be. The cuckolding fantasy -- that a man who either "allows" or who "can't stop" "his" woman from being with a stronger, harder, bigger, more dominant man is therefore less of a man in comparison, is humiliated, emasculated -- can ONLY exist in the context of these gender tropes. In reality, the size of his penis or how hard he fucks does NOT make a man more or less of a man (that's the assumption that's anti-gender-equality), nor does letting his partner freely express her sexuality with another somehow make him someone who is powerless or impotent (that's the assumption that's anti-sex and anti-poly).
To *pretend* that any of these things are true because they can have an incredible erotic edge to them to people raised in a society steeped in these tropes is fine as long as everyone understands what's going on, has given consent, and understands that they're free to step out of the fantasy at any time. That's the paradox and the beauty of kink, you get to take what can be some really "wrong" urges and safely explore them for fun and profit (by profit I mean orgasms).
If we fail to acknowledge the line ("I call myself my partner's slave, but I'm actually free to leave any time", "I pretend to rape my partner but I would never actually do anything he didn't want me to do", "I savor the role of cuckold because it turns me on but I know there's nothing actually humiliating about being exactly who I am") we not only give others a VERY bad impression of what's going on, we also run the risk of damaging ourselves and/or our partners by losing sight of the "sane and consensual" parts of "safe, sane and consensual" kinky play.
Sorry for threadjacking, OP!