Originally Posted by Marcus
I agree, if you love someone you should not want to be party to their living a life they do not want to live. This applies to you as well, why would you want him to live in monogamy if he has made it plain that he has absolutely no interest in living that way..
I agree with Marcus, who wrote this, and SchrodingersCat who also quoted this. You and your partner are not compatible. That's fine. I know you're upset about it, but the good news is you now know you're incompatible.
The best thing you can do for both of you is to end the relationship as it is now. Set him free to be poly, and set yourself free to do what works for you. I applaud you for knowing who you are. That will put you in a much better place in the future (in your own life) than your partner will be in his life.
Your partner has some struggles ahead of him that he doesn't see coming. He wants to experience more women because he is afraid of experiencing less women. That is not a good foundation for a relationship with any woman. He will find women, but there will be a lot of drama because your partner and the women he finds will focus most of their attention on what they can get from each other, and very little on what they can give to each other.
He is literally telling you you are closed minded because you are monogamous. That means he is telling you that you are closed minded because you are different from him. Right now he is in a monogamous relationship with one person - you. You know from your experience with him how well that attitude works.
He will bring the judgement of "you're wrong because you don't see things the way I do" into the more complex environment of multiple relationships. This attitude will bring a lot of drama into his life until he learns to see value in the choices others make that are different from his own. By ending the relationship with him, you will be able to step out of the way of the struggles that he would have otherwise brought into your life.