There are several things. I was a "serial cheater" before my fiancé, it never crossed my mind that my previous boyfriends would accept my idea of "How about I get to fuck whoever I want and you can't?" Hahaha. It sounds counterintuitive and that you're not so lucky.
Because you know those kinds of men exist, but you never believe that yours is one of them. Just as most men do not even dare to mention an FMF threesome to their women, simply for the fact of being frowned upon.
And it is worth thinking about, we must be careful with what we say and who we say it to, it can completely change a person's perspective of you. For example, tell a female friend that sometimes you are curious about giving oral sex to a man, and you will forever be a sissy in her eyes, and u know it.
And when a woman is questioned about this, I have to say in defense of those who refuse, that the topic is always approached very poorly. Normally the guy is not tactful when he brings up the subject, this is something that will change the relationship and the guy, guided by his cock, he wants an immediate, accurate and satisfactory answer. Something like:
"Of course I want to fuck others as a slut, but I will continue to love you without a hesitation, this will never change things, I will only do what you want, it will never cause problems or doubts and I will always ask you before, and you can blame me for what I am saying now and whenever you want or I get out of line a little."
And of course it's ridiculous to think that.
Sex is complicated and will surely cause problems, and women know this better than men. I'm not saying it always has to be a disaster, but cucks go crazy as soon as something turns out a little different than they imagined.
Finally I have to say that cucks are selfish by nature, it's ironic I know hahaha I'll explain it. They want things to be exactly as they always say, they feel free to set rules and limits and not accept any of the other two parties. It's not going to work out like that, the girl and the bull will surely break rules at some point, sometimes because it's fun, sometimes because the situation is beyond your control.
The thing is, the cuck must be willing to talk this out and not go crazy and claim that his precious, priceless trust has been broken. Just as fights happen in a vanilla relationship, they happen in this one, and most of the time they are resolved if they talk calmly.
And if I thought all this for an answer in this post, believe me she will think it too.