My Dad has really poor social skills. I have a whole lifetime of experiences I could write about (!) but I will try and be brief.
He constantly judges and criticises other people. For example if we were in a restaurant and there was someone overweight he would make a comment like "look over there at them stuffing their face". Or he could see someone in the street and would say something about their appearance. He mainly criticises women which is a great example he has given to me and my sister growing up (!) It is really, really rude and hurtful and we always tell him to stop being so horrible but he never does. My DSis, DB, DM and I avoid going to places with him as much as we can. However, my sister and I went on a walk with him during lockdown as we knew there would not be many people around. However he instead criticised people's homes, cars and front gardens - "their house looks a mess, so rundown", "their front garden looks stupid". It is summer, a lot of people would had their windows fully open so they likely heard him. If I or anyone else tell him to stop being rude or to be quiet he raises his voice deliberately to embarrass us and tells us to not tell him what to do. He does not comprehend that other people can hear him or that if he must make such horrible comments he should whisper or lower his voice.
Even aside from the cruel comments he makes, he is uncomfortable in all social situations too like when we went to a family wedding he wanted to go home straight after the ceremony, or when we visit relatives he will either stay home or make us leave after very a short time. When we had family or friends visiting our home (pre-lockdown) he would always go out. He is also really poor at making eye contact and struggles to make conversation. If I ever try and talk to him about something I just get "hmm" in response and that's it and I can tell he is not really listening to me. He doesn't participate in any of our family celebrations like he never comes to restaurants when we are celebrating a family member's birthday, graduation, engagement, etc. It is really quite hurtful.
I just do not understand the cause of it. I cannot interpret why he acts that way. I understand that you could just say he is a mean person but I feel like that paired with the lack of social skills implies something more like an actual condition?