Myself and my friend were taking the piss out of each other in the groupchat as we always do, he calls me fat and I call him skinny etc. it’s all jokes though, we’ve known each other for years!

Anyway our other friend got extremely offended over me calling my friend a skinny prick, saying how it affected him because he’s also skinny. I don’t understand why he got so offended as 1. It was just banter and 2. It wasn’t aimed towards him at all... what do you think?