Sounds as if we are confusing swinging and/or an "open" relationship with BDSM. I have heard of people who are into inflicting pain or receiving without having sex. In my experience it has usually been the "subs" who claim it's not sexual, lol. But anyway it takes all types. Public BDSM to me means going to play parties and participating in the BDSM community. It's not for everyone. Many, perhaps most, prefer to keep it private. Some people have a more exhibitinist side to them. It's sounds as if your partner might want toexplore the exhibitionist aspect of BDSM. Swinging and sharing of "subs" can be part of the BDSm expetrience, but is not the norm. I would say most subs in long term romantic relationships , especially women, do not desire to be shared or to have another parttner in the relationship. Many "Doms" try to use this as a way of having another sex partner on the side. If your guy claims that sadism is not sexual for him then this might be a way for him to have a masochist sub/play partner but with whom there will be no genital sex. These are all things that should be thoroughly discussed with both partner's feelings taken into account. We don't do anything that we don't want to do. Sometimes a "Dom" just has to hold back some of his wishes.