This is not really a swinging issue, since your husband offered it as some kind of weird compromise that he probably knows won't work, since you say you have no desire to have sex with other men.
The way I see it, you have a few main issues. The first is kind of academic: what is "rational" or "irrational" in this situation? Are you rational to want a monogamous marriage? Is he irrational to demand to be free to pursue dating other women? I think it would help if you can actually articulate why you don't want him to date other women, and if he can actually articulate why he thinks he needs to, or at least explain the desire.
For your part, I think it's important to put aside the *societal* expectation of monogamy being the norm and "of course" anyone who wants an open marriage is automatically in the wrong. Forget about society. Why do you, rose_bleu, need your husband to forsake all others? This is a very important question, and one that may take a while to get to the bottom of. You could try to answer the question of what specifically you think you would be losing if your husband pursues his desire for variety. Is the problem that you think you might lose him to another woman? Or lose more of his time, or his attention, than you're willing to give up? Or perhaps you simply believe deeply that married people should sleep only with each other? Your original post said that your current opinion is that monogamy is the lifestyle for you, after having some experience with other lifestyles. Maybe you will come up with different answers entirely.
Most people in society "know" that married people should only have sex with each other for the health and stability of the marriage, and they "know" that a desire to have sex with others is an affront to them and their status as spouse. As swingers, we have come to believe this is not true. But swingers (by and large) also want both spouses to have the desire in more or less equal parts, and also to (mostly) participate together, couple to couple. Personally I don't think that is the only right answer. The right answer is some arrangement where both partners feel they are valued and happy in the relationship, and confident of its strength. If it sounds like I have spent some time thinking about this, you're right.
For your husband's part, he needs to reach deep inside and explain what is motivating him so strongly to believe he needs to be "off his leash" or feel too caged to continue in a happy marriage. Is he looking for outside validation? Does he crave attention from new women for the excitement? Is he afraid of getting old, and needing to cram in all the "dating" he can before his time expires?
My opinion is that perhaps once you have the answers to those questions, you could make headway on who is being rational or irrational. But that may not matter so much as the below.
The other, more important issue is that you have what *could* turn out to be an irreconcilable difference, regardless of whether either of you comes to think of either position as rational or not. You need your husband to not date other women to be happy.. He needs to be free to date them in order to be happy. From what you write, he feels he doesn't have a way forward in the relationship unless he has this freedom. Also from what you write, you are not sure you can continue unless he agrees to stay faithful. By the way, if he does agree, I believe you are setting yourself up to find out one day that he is cheating. That urge for sexual freedom drives people to do things they never thought they would or could do.
You two love each other, your sex life is good together, and everything else seems to be a go in the relationship. I hope you can find a way past this. It has already been difficult for you, and finding a way that you can both move forward and feel positive about your marriage will be a challenge unless one of you comes around to thinking about things in a different way.
I hope you will continue to check in and let us know how things are going. I don't know you, but my thoughts are with you.