If this is not something you ever imagined doing, and you can’t imagine feeling comfortable with it, then it’s hard to imagine continuing to be with him. I think he is doing you a favor in telling you what he wants before you go any further. He is doing the honorable thing. I hope you appreciate that.
It sounds like you have different expectations. You seem like you want him to be dominant—at least in regular life. How has he treated you otherwise? Does he take the lead, or are you always kind of sitting there trying to figure out what you want to do? In any case, whatever his style is when you’re not talking about sex, I wouldn’t expect that to change much after you have sex. It’s too exhausting to pretend to be someone you aren’t in real life.
These kinds of sexual games are about fantasy. Remember that the brain is probably the greatest sex organ. Fantasy is different from reality, and just because you fantasize about a thing doesn’t mean you want to behave that way in real life. Usually these things are done with a lot of rules, and with great concern to keep you both safe, so that neither of you goes into areas that make you uncomfortable (unless you like that), or that will hurt you.
Have you ever fantasized about being dominant? Could you? Personally, I’ve never done it in real life, and I’ve had limited fantasies about it because usually I prefer equality. However I was once with someone who was into it, and I indulged her fantasy, and I didn’t mind at all acting like a jerk once she told convinced me that she really wanted me to do that. It’s not something I would do, however, unless my partner really begged me to do it.
I don’t think it’s a bad thing. I don’t think it is dangerous if you follow the rules. However, you don’t seem comfortable with it, and that would cause problems down the road, if you are not open to it, and he continues to fantasize about it. If you don’t want it, and would be really uncomfortable even trying, then he’s doing you a favor. Be friends or break up or whatever, but don’t get any more deeply emotionally involved with him.