But I was not thinking of coercion...
Ok, I'm going to reformulate: imagine that you have just finished having amazing sex with the woman of your life, the one you have been with for years and that you truly love. Let's suppose that she tells you that lately she's had this hot fantasy of her in which you perform homosexual stuff with another man while she just sat there and watch. She tells you that she'd like to see you make out with a guy, or give each other a handjob or even swapping blowjobs... she's not forcing you at all. She's just telling you that she'd get really hot if that could happen. You can't leave or get mad at her for just expressing one of her fantasy, as strange and awkward as it could be, right?