I think a big reaction is probably normal. I mean, seemingly out of nowhere he finds out that you want to completely change the parameters of your relationship. Combined with your history of cheating, he probably has a lot of thinking to do about what he wants to do.
Why not let him know you understand that he needs time to process, but that you think it's unfair for him to refuse to the see the friend? You could offer to give them a couple of hours to catch up without you being around, that way he doesn't miss out on an opportunity to see someone he cares about because of the stuff going on with you. I would think showing some understanding about what he's going through at this time would help him remember why he's with you in the first place and could help him accept that the conversation needs to happen.