I'm kind of irritated

So..a few months ago, my fiancés "friend" snap chatted me some inappropriate pictures, asking for some in return. I acted like I hadn't seen what he sent me and asked him to resend them, in the mean time getting my fiancé next to me so he could see when we opened them what they were. My fiancé didn't seem to care much because he trusts ME and says that's all that matters. I then deleted his "friend" on all social media but to this day I still see my fiancé and him interact with each other...and I'm sorry but it bothers me. He deliberately sent me dick pictures that he shouldn't have, knowing damn well I'm in a relationship with his "FRIEND." It's great my fiancé trusts me enough to know I'm faithful but I can't help but feel he should still be upset with this guy! Instead he acts like nothing happened. Wtf?