Sorry in advance, English isn't my first language.
I [28M] have been with my boyfriend [33M] for the past five years. He comes from an extremely religious family, therefore he hasn't come out yet, not just to them but entirely. The only people who know about him are me (obviously), my first stage family, some of my close friends and his mother, who he told a few months ago and haven't talked to her about this since (at least as I'm aware of). He is currently studying medicine, and because of the high demand and time consuming studies he doesn't have much time to work, therefore still lives with his mom, stepdad and youngest brother who is 10.
All his family and friends know me as his "best friend" for the majority of our relationship and really bonded with me, and I'm with them. I often come to their house for dinners, go out with his friends and relatives and even been to a couple of his family weddings, all that without them knowing about the true nature of our relationship.
Last Thursday he got into an incredibly heated argument with his stepdad. He made an honest mistake without knowing and he got scorched for it, hard. I wasn't there for it, but from what he'd told me he was in the car with his friends, about to go to the movies, when suddenly his stepdad started screaming from the window at him to go upstairs and fix the mistake that was discovered at the time, that again, he wasn't aware of. He was extremely embarrassed since his stepdad was utterly rude and disrespectful and shouted at him so loud that their neighbors started looking outside their windows. After he fixed what had to be fixed and went to the movies, he sent his stepdad a really nice text (which I read) owning up for his mistake, apologizing and taking responsibility for his actions. He also wrote that he expects his stepdad to do the same, owning his mistake for embarrassing him in front of his friends and neighbors, and the only response he got from him was "You idiot". He was of course deeply hurt by him and called me for support. I of course took his side and said that his stepdad was overreacting, but that's on him and he shouldn't be taking it personally. Demeaning someone on purpose over an honest mistake is much worse that making it. He was still hurt of course and was really affected by it.
The next day I went to his house for a Friday night dinner with his family, a thing I haven't done a few weeks at that point. I could feel the tension in the air and that he was a little off, so I tried to stay close to him and distract him, while being nice and polite to all his family members, including his stepdad (which is quite fond of me to be honest). For context, I recently got a place of my own after living with my parents until now.
During dinner, his stepdad asked me how's my new place and I said that I love it, which I do. Then he asked me "Don't you want to take him (my bf) with you? Don't you feel alone?". The first response that came to my mind was "Well I already asked him and he said no", which was true. During the process of moving out I consulted with my boyfriend and asked him if he wants us to live together. He said that he couldn't support himself financially on his own at this time of age because of the reasons I mentioned above, and I completely understood. I still wanted to move out from my parents though, therefore got my own place eventually. Anyways I didn't say all this out loud of course, but instead tried to deflect and said that I don't mind being alone, and that I also might not be for long since I'm planning on getting a cat. He (the stepdad) said "well he (my bf) also likes cats" and than continued the conversation. At this point I started feeling very uncomfortable and just smiled and nod at him, avoiding eye contact until someone else changed the subject and dinner continued as usual.
When I got back home I got a text from my bf asking how did I respond to his stepdad, since once everything started he got off the table and played with his nephews to remove himself from the situation. I said that I tried to ignore him, just smiling and nodding until he got everything out of his system. He asked what are my thoughts of what he said, and I told him that I honestly didn't get what was the point of it all - he said everything with a half smile so I couldn't figure out if he was serious or not and what was the whole point of it, and it was honestly just weird. He then accused me of playing naive and choosing my words carefully and said that the purpose was to hurt him, whether he was serious or not. I replied that I didn't give much thought about the subtext of it all because he wanted to hurt him, and I didn't want to give him the satisfaction. I also said that I'm sorry he has to put up with this kind of bullying in his own home. He said that he shouldn't have had to squeeze that reaction out of me, and that I should have replied, especially since I noticed he got hurt and got off the table, which I did. I explained that he (the stepdad) hit a nerve for me about our joint living, and that I'm not a confronting person, especially when the situation doesn't involve me. I also said that every time I'm in his house I have to put on a mask and be aware of every single word that's coming out of my mouth (a thing that I mentioned to him multiple times and one of the reasons I don't come as often as I used to), and because of the delicate subject I couldn't think of anything of the top of my head. That no matter what response I had come up with, he would have find a way to twist it and I thought it's just better to ignore him. He said "Seriously? you see someone hurting me and all you think about is yourself and how it affects you in this situation? and you couldn't even let go of it?". He also said that I should've reacted to show that I care about him, and that that's his expectation from every close person to him in that situation. I than said that I think they should talk face to face and that in addition to bridge the gap between our differences, this conversation is also a way for releasing the anger he already has on his stepdad, which is okay. He said that his stepdad is not a person to have that conversation with and that he's not using us talking to release anger, but to express the fact that he was feeling alone in that situation. I kinda felt like I was left alone in that situation, but I wanted to validated his feeling instead of deflecting them, so I wrote back "I'm sorry that I made you feel that way", and I really meant it.
The next day when we were talking I could feel he's a little distant and maybe even still angry with me. This is also not the first time something similar has come up, because this sticking up for him thing is a delicate subject for him because of past traumas (according to him). There's still much more relationship context that can be given, since our situation is sooo complicated, but I keep replaying the situation and my response to it, during and after, and I really feel like I tried and did my best with what I had at that moment.
Yet I can't help but wonder.. AITA for not sticking up to him more in front of his stepdad?