You seem to completely forget about the kinds of vitriol you've been posting yourself for maybe weeks on the chat over there. I've personally seen very aggressive comments and inciting rants, as well as quite rude behavior repeatedly. For instance, you have a way with profanity on occasion that I'm sure is offensive to quite a lot of people -- including the ones you "scream" insults at -- yet you want to pretend that you're some sort of victim by having others say something offensive to you.
As usual, there are many sides to every story. It's ridiculous that you are drawing a line with this joke and thinking that this exchange the reason you were banned. There were many complaints about your behavior over time and I'm not sure why you're so confused. The same type of complaints you have against other chat participants, who are also NOT banned for their behavior, are the types of behavior you have also exhibited. I don't like racial jokes either, but neither do I enjoy insults I've seen you spew. You were not banned when you did that for weeks.
An obvious -- and self-admitted -- spam bot is certainly enough to get you banned in many chat spaces. All the other definitely-annoying exchanges on the site chat were tolerated just like dozens of other annoying chat exchanges are tolerated. It's a very open chat space, which is an understatement. Some people don't like that, which is fine.
Why am I still typing? (Why did I start typing?)