AITA for giving my wife and MIL the cold shoulder after they criticized my sister?

Update - I ended up flying my sister to my house for Christmas, and spent some time with her before flying her back out to Seattle. My wife and MIL were noticeably uncomfortable during her visit, and I refused to let them talk shit about her in my house. I think they learned their lesson.<br><br>I have a younger sister, Kate, who is a talented artist. She never wanted to go to college and instead decided to focus on painting and drawing as much as she could. I fully supported her decisions because that’s what family does. We are very close and in the few times my wife and MIL have met Kate they have always been very critical about her art and life choices.<br><br>I recently won a partial scholarship to an Ivy League college to get my MBA, and I fully expect to find a good job after I graduate. My wife and MIL are thrilled about the opportunity, and I was prepared for them to offer some sort of congratulations. But instead my MIL said that they were “naturally more talented” than Kate, and that it’s great that I didn’t follow in her footsteps. My wife joked that Kate would end up living with us. They both laughed about it. <br><br>I wasn’t about to let them get away with this. I told them both that if they ever spoke about Kate like that again, I would “eliminate” them from my life. They tried to argue but I wasn’t having it. I stopped talking to them and moved to an empty room. I told them I didn’t want them in my life if they were going to speak poorly about my family. They are still angry with me about this and think that I am an asshole for telling them to shut up.