AITA For refusing to call my coworker his preferred nickname?
So I work in an office setting. It's pretty formal. Generally people wear shirt and tie. One of my coworkers is a pretty big sports fan. In particular, this quarterback Jacoby Brissett. I'm not a big sports person, but my understanding from talking with people around the office is that Brissett is pretty mid. Not according to this coworker. He talks about Brissett all the time. How good he is. What a game he had last weekened. It's the offseason right now, but he still talks about Brissett. Wondering what kind of workouts he does, what he eats, fantasizing about running into him at the supermarket (we don't even live in Arizona where he played last season, which I only know because of this guy).
Anyway, this coworker doesn't call him Jacoby or Brissett. He calls him Brisket. Like the smoked meat. He thinks it is hilarious. I hear him talking about Brisket all day. And the first time I hear it everyday I'm still confused, thinking he is talking about food. He even got a custom Cardinals jersey with Brisket name on the back. And it doesn't even look like the real jersey. It's tan and looks like someone took a bloody shart on it. Now he wears this jersey every Friday, claiming it's casual Friday, which we've never had before, and bringing the whole office into disrepute. When I mentioned this, he said Brisket is the greatest NFL quarterback ever and if anything, wearing a Brisket jersey is more formal than anything I wear, even on the day I wore a suit. He's wearing the jersey multiple days of the week, even if it is visibly stained. He says the jersey is a counterfeit and if he washes it too many times it might fall apart.
Here's the kicker. Now he wants everyone to call him Brisket. He won't respond in person, meetings, or groupchat unless we refer to him as Brisket. I feel that we have to draw a line in the sand at this point, but other coworkers worry about upsetting him because he is still really productive and also he has been bringing in homemade brisket now which is admittedly really tasty. What do you guys think??