AITA for telling my fiancé his mom posts thirst traps on instagram to get likes and attention from men?

I (30 F) went to the gym this afternoon. Usually, my fiancé (31 M) and I go together, but he was sick so I ended up going by myself. When I was done, I called him so we could talk while I drove (we don't live together yet). During the call, I was telling him I posted an insta story showing my legs even tho it was upper body day because I was wearing a hoodie and so my arm muscles would not show. It was just a random and insignificant comment, but then he started telling me (as a "joke") that I did it for male validation/attention. At first, I laughed and ignored the comment, and said that I liked how my legs looked. He continued "mocking" me saying I needed other men's attention and posted to see if I "caught something" and blabla. I got upset and "jokingly" replied with "your mom". He said "what?" And i said "your mom posts pics to get men's attention and likes" basically what he just said to me. This is COMPLETELY false lol and I absolutely love his mom, I just wanted to make a point and for him to realize that what he was telling me was offensive and rude. He immediately told me not to involve his mom and that he would hang up on me. I said "see? It's not a nice thing to say right? You don't want me to say that about your mom but it is okay for you to say it about me?" He said he was not offennded, he just didn't want me to involve other people. I told him he knows it was a rude thing to say, otherwise he wouldn't be mad I said the same about his mom. He kept saying I was wrong and that if it was a lie, I wouldn't be so offended. I hung up on him because I was so mad. I expected him to call me back immediately to apologize, but he didn't.

Was I the asshole?

PS. My picture was not even bad or revealing. It was a mirror selfie and I was wearing a hoodie and shorts.