AITA for ruining thanksgiving?

So my sister in-law(F23) and brother(M35) got into a huge fight over a haircut. He went away for the weekend with some buddies and while he was gone his wife went and got a pixie cut. When he got home he was livid that she had cut off all her hair without asking him. He didn’t want her to have short hair he liked it long. They went away for the weekend again to a couples spa and when they got home the sil had gone to a barber and had all her hair buzzed off. Bro was super mad because he said she went behind his back. <br><br>This went on a few more times until he just took her phone to stop her from going. He went to the appointment himself and it was a surprise to humiliate her because she had asked for a “feminine buzz cut, short on the sides only leaving 2 inches in the middle and to make sure it was messy on top to show off her face and make her look beautiful and feminine” And that’s exactly what she got and when he saw himself in the mirror he flipped shit and she yelled at him for making her go through all this shit just for him to get her the haircut she wanted all along. He has spent the last 2 weeks pouting in our parents house so he could get away from his “stupid, abusive, manipulative bitch of a wife”.<br><br>We are a big family(8 siblings, spouses, and 26 nieces and nephews) so Christmas and thanksgiving are big events hosted at our house. Each person/couple brings a dish. The last 2 years my brother hasn’t brought his wife. He says Thanksgiving and Christmas are important days for the men in the family and he doesn’t want her agenda to over shadow our heritage and traditions. My sil is very feminine but she is also part of an antifa organization i think is what he called it? Idk I don’t care about politics. But he just doesn’t want her ruining our holidays.<br><br>This year was the same but sil showed up with a big dish of stuffing and when he tried to stop her from bringing it in my husband and his brothers stepped in and said traditions are important but family is more important and if he thinks excluding her is keeping a tradition then he can GTFO. So we ate dinner and he pouted the whole time.<br><br>After dinner the kids went to play video games and we sat in the living room to talk and my sil brought up women’s rights and women empowerment and my brother told her to be quiet but she kept going. He yelled at her and she yelled back and he grabbed her by the hair but it was short so he grabbed her face and her glasses fell off on the floor and he dragged her out by her ear. I followed them outside and he had her by the throat when my husband and his brothers came out and hit him until he was on the ground screaming. He hasn’t come home since.<br><br>His friends and some of my siblings have been texting me that I should not have let it get that far and that I should have stopped her from bringing it up because I know how he is and it was my fault that thanksgiving ended in a fight. AITA?