Ok, I've name changed for this, because I don't necessarily want this connected to my other posts.
There's a whole lot of kink shaming going on in this thread. As someone who would be classed as a 'masochist', I seek out those who identify themselves as sadists.
I am, as far as I'm aware (or anyone who knows me in day to day life would consider) a very nice, normal, well rounded person. I save lives for a living, and enjoying pain doesn't make me a bad person, or any less good at my job, or mentally unstable etc etc. When something hurts, you release endorphins, biochemically, the feeling of pain is incredibly similar to the feeling of pleasure. I've been known to orgasm from pain alone. But for the most part the endorphins make my brain quiet, it's like a factory reset. I relax, the tension leaves my body, and my brain is still. The emotional aspects of sadism are also really peaceful. All of it, physical and emotional, is within my control. As someone who experiences lots of physical and mental pain, that they are not in control of, it's liberating to seek it out in a way that I can make it stop when I want it to stop.
As someone with ADHD, a really tough home life and a high pressure job, it's the only way I've found to give myself a moments peace. And if you've ever had to try and revive a baby while the parents are screaming behind you not to let them die, and then gone home to your own (very ND) children and tried to slap on a smile while they complain about anything and everything, you'll know how needed that peace is. Sometimes instead of peace, I'll cry, and honestly it's such a cathartic release, I feel so much better afterwards.
All of the 'sadists' that I engage with, are genuinely, without a doubt, some of the nicest humans I have ever met. They are kind and considerate, and do what they do because they not only enjoy an element of control (for whatever reason, they all differ) but mostly, because they love that they can create a space for me to feel safe enough to disengage with the world and put myself in their hands for a bit, and they take that incredibly seriously. They only have interest in hurting me as much as I want to be hurt, and always make sure I'm on afterwards, I often phrase it when talking to others as wanting someone to break me into little pieces, but I also need to know they will piece me back together again when they are done). Their pleasure comes from me getting the pleasure I need from it, not because they have hurt me. Never in a million years would they engage in that way with someone who didn't want them to, and there are enough of us who do that mean they don't need to do it with those who don't.
Obviously, there are plenty of abusive men who I wouldn't touch with a barge pole, and I can't tell you from here which one he is (I probably could with about 10 minutes in the same room with him to ask some questions!) but I think it's a leap for everyone to assume he's some kind of heathen or a psycho.
But more importantly, as someone else said, this is unlikely to work. You aren't interested (which is completely fine!) and he's unlikely to suddenly not want this. At best, if he's one of the good ones, the relationship won't survive, or he'll always feel like he's compromising, at worst, he isn't one of the good ones and either cheats or starts to try to push you into it. None of them are winning scenarios.