Why do some people find insulting jokes funny?

I don't like them at all. It's demeaning and horrible. One of my younger cousins did one to me. He said, "Hmmm....queen of comebacks huh? Well if I were one of your friends, I would have read an article about you and realize you suck at it. Did you forget your middle school grammer?"
People were like, "DAMN!!!!! Savage." I was shocked. She kepted roasting me and my best friend was like, "Are you going to take that from a 13 year old?! She is roasting the hell outta you!"
Since then I hated her.