Stupid

Why does the word stupid bother me so much ? My partner says it to me not a lot but enough to where it bothers me. And not in a joking way. He doesn't say it violent either. But today I told him that the air quality is bad and covid so I don't think we should take our 1 year old with his family. He joked and said, break the news to them. They want to go Saturday. I asked him again if he was going to tell them with time or if I should (I'm close to his dad, he has treated me like a daughter since I was 18 when my dad wasn't in the picture anymore) I was just going to let him know that his grandson and I won't be attending. He got all mad and said its none of my business and its him and his family's business and I kinda understand but not really . It's also my business because my son and I were invited (he probably thinks I'm going to talk to his mom who doesn't really care for me. And his sister who is fine with me) but anyways. Then he said I understand, which I wanted him to clarify what he meant by that and if he really wants to not have me talk for myself and then he tried to say that I'm really stupid if I don't understand what he's trying to say. (He knows that the word really bothers me in the sense that hes trying to insult me on purpose because hes mad at me). But I got up and cried. And this time it wasn't because I think im stupid because I am not. But because he knows how its made me feel. That he'd go to those.lengths because we argued.