I was humiliated by a flight attendant. I was sitting in an exit row with a seat belt extender, not knowing this was a problem. This particular flight attendant watched me get into the exit row seat and didn't say anything. We were settled in, checked by 2 other flight attendants for safety protocols, and about to take off when this flight attendant came up and very loudly demanded to see my seat belt. She asked loudly if I was wearing an extender. I replied I was and she starts very loudly telling me that it was a felony, that I was going to receive a penalty, and needed to move. She then proceeds to call out to the entire cabin asking if anyone could take my spot... This flight was not full, she could have just quietly asked me to move. My mother was with me and she said she would move with me and so then she's calling for two people to replace us saying we are not allowed to sit there. She then demands my seat belt extender and argued with me about keeping it. Did she want me to sit without a seat belt at all? It didn't make sense. This was in front of everyone and was humiliating. She later came to me and told me again over and over that it was a felony and said that because she is a large woman, she looks for these things more often and understands. You would think if someone understood that they would go out of their way to be kind about it. She was extremely rude and embarrassing. I am not exceedingly large. I fit in the seat fine and sometimes I just need a little extra slack on my hips. This woman is a large woman and clearly has some hang ups about it. I understand that there are protocols and rules and don't have a problem with that. The way this was handled was appalling and humiliating. I was literally forced to tears out of embarrassment and people around me were clearly very uncomfortable with the situation. This could have been done quietly and politely informing me gently that I needed to move. I am just so disappointed in the service and behavior. I fly regularly and have never ever encountered something so degrading or embarrassing. This flight attendants name is Rebecca.