AITA for not wanting to stay at my sister’s house because I don’t like her fiancé?

My sister (28F) has two daughters (6 & 12) from a previous relationship that she has asked me (20F) to babysit on two occasions. She lives with her fiancé (36M) in a house that he is currently renting out.

The first time I stayed at her house it was only for two days and didn’t run into any issues with him as we only spoke a bit. He shares very different political views from me but I didn’t care because I was there to spend time with my family.

The second visit was different.

I was in the living room talking to my nieces when he came back from work. He didn’t say hi to me but instead he made a snide comment about my acne. It threw me off how he was making a joke about my face when he hadn’t even greeted me nor does he know me like that to say that type of thing. What bothered me even more was when my sister awkwardly laughed along. I got embarrassed but I tried to laugh it off. I was going to help my sister clean, but after a couple of minutes of waiting for her to get the vacuum her fiancé told me to start cleaning. I thought he was joking so I played along and told him it was too cold. His faced dropped and he started going off on a tangent about how he’s spent the whole day outside in the cold working.

He killed my mood every time he’d speak to me. For the rest of the time I was there I tried my best to be nice but he’d make racist jokes that made me uncomfortable since he expected me to laugh along and would ask me questions about sensitive topics that I know he just asked because he wanted to get a reaction out of me. I just didn’t feel welcomed by him. I understand that it’s his house and I am a guest but if thats the case he could’ve been a bit more friendly or at least not as hostile.

About a month after that visit, my sister came over with my nieces to go out and spend time with my mother and I. We got lunch where she asked me to stay the week at her house. I said no as I had many times before ever since that visit. She finally asked me why until she mentioned it being because of her fiancé. I didn’t deny it and she kept egging me on and asking me why I didn’t like him. I flat out told her I didn’t like his attitude and she called me weird and started getting aggressive with me.

She brought my niece (12) into the conversation and said “you like him right?” and looked to her for confirmation. She stayed quiet and mumbled something incoherent but I’m pretty sure her answer was no. My sister started going off on her telling her to “say it with her chest” if she doesn’t like her man. This pissed me off because I could see my niece holding back tears as my sister berated her. I called my sister a bitch and told her to not speak to my niece like that. She just ignored me until it was time for her to go back home.

I am not going to willingly place myself in an environment where I feel uncomfortable and not welcomed. AITA?