So this past weekend my fiance and I moved into our home. Both families came to help us. My fiance has never cared for my sister but always put up with her for me. Well this past weekend my fiance asked that my parents not bring their 3 dogs to the new house. My parents, who came from out of town to bring us furniture and help, didn't have anywhere to put the dogs all day other than my sister's apartment (an hour away). Since we would all be working all day they said they needed to bring them. My fiance and I agreed that putting them in the basement was a good compromise. Well, after the dogs were down there, they started barking and one clawed the door. My future MIL started yelling that the dogs were scratching the door and the house was stinking of dog. (mind you she has two huskies). This upset my fiance who was already on edge.
My sister started to defend my parents needing the dogs here and I defending my fiance not wanting them in the new house right away. In typical fashion for my sister, she mouthed off to me (reason my fiance doesn't like her). My fiance then yelled at my sister, defending me (even though I didn't need him to). My mom wanted the fighting to stop said to both of them "Stop fighting." My fiance took it as my mom defending my sister's actions. He stormed off. He now wants me to choose between him and my sister. I can't do this, but he is threatening to walk out. What do I do?
Oh and to top it all off my future MIL told me and my parents that he would easily walk out of the relationship because he can't stand my sister. Saying that I don't matter to him at all. I was in complete shock and now my parents are angry and feel she disrespected me (which I agree she did). How can I now address this issue? My fiance is siding with his mom here.