Hmm, I am going to be honest and say you seem defensive, which you have every right to be, but I'll point out that if you were my partner and reacted like that to me in a discussion or that attitude was coming through in your tone, I'd be put off and closed down.
Of COURSE your voice matters. However, if somebody is put off strongly by a certain experience (my mom was a swinger, I am very put off by the idea of a partner asking me to do that, and would dismiss it out of hand), even if you find it something you'd like, just realize that it's not likely you will get them to want to agree to it. Let's say she specifically asked for a MFM triad, if you KNOW you don't want to be in a MFM triad where you have sex with her boyfriend, I imagine you'd just say "No I don't want that" and not be interested in further discussion?
That's why I suggest the book, and exploring alternatives to what you suggested. It's also why I suggested the phrased response I did, it opens up the conversation again and gives her the opportunity to respond to what you wanted even though she closed down and didn't address it before. Hopefully it gives you both a chance to remember that you're both coming at this discussion from a place of loving each other (or I hope you are) and to not close down or get upset with each other, but to be able to calmly discuss what you and and how you can both compromise to both be OK with the situations...OR at least to realize that you both can't come to common ground and make decisions based on that.
Happiness will never come to those who fail to appreciate what they already have.