Why does this bother him so much?

Ok this is a question for the guys, I have a man I’ve been dealing with (not in a relationship) but that’s the kind of role he plays in my life. He does a lot of what a boyfriend would do for a girlfriend but we aren’t officially together. Anyway, since we aren’t together, I told him there’s a guy at work that likes me and wants to have sex with me and I was asking him how he would feel if I did anything with said guy. Well I basically got crucified for even letting that come out of my mouth. For context, he used to talk to other girls in front of me, do sexual things with other girls etc, and it made me feel bad like I was jealousy. But he would always say he didn’t want the girls, so I’m like if you don’t want them why are you giving them your attention? Make it make sense. So now that the tables have turned and I was considering for a minute sleeping with another guy he feels like I’m not really down for him and to not say things about how I love him and want to marry him. The guy I wanted to sleep with so basically he’s more sexually open than the guy I’m dealing with like likes to do everything you can possibly do to a girl and it piqued my interest. The sex is great with the OG guy but we do the same thing and then it had been almost a month since I had any because he had been away. But I made the decision to not do anything with the other guy and he feels like I still disrespected him by even thinking of doing it. So guys why is it ok for y’all to do it but when it’s in the girl’s court doing it to y’all it doesn’t feel good? It’s basically that saying “it ain’t fun with the rabbit has the gun”. We aren’t together and he doesn’t want to make me his girlfriend so if I had slept with the other guy he can’t say I cheated. I’m free to do what I want I just choose not to out of respect for him.
Why does this bother him so much?
Post Opinion