What should I do about my marriage?

I have told my husband that I do not want to "make up" with his sister or his aunt after a tirade they had with me over something that was none of their business. This has gone on for over 8 months. They said very hurtful things and I wish to have no more to do with them. I have no problem with him talking to them. They are his family. However, we are not invited to anything and he won't go without me. He got angry last night and told me that I either go to mediation with his sister about this, or he will divorce me. I could not believe this. Not only has he not told them off for treating me like this, but now he is threatening divorce. I love my husband and cannot believe his stand on this. I don't know what to do.