You apparently insulted them through the chat. It's pretty hard to detect sarcasm or joking around in the way you were doing it in a chat box. I'm not saying you were the worst person in the world for saying that, but apparently they took it differently than you meant it. They may be a little sensitive, but they have a lot of people actually making fun of them throughout the day. They may just have been having a bad day. Sorry you got banned, but it is their channel, and they have the rights to do whatever they want on their channel