It's very hard to get fired as a union pilot for a major U.S. airline these days. A few people do succeed though.
As a former union rep at a major carrier I agree. But this captain might have just managed to do so with this one.
Although, JetBlue wasn't union at the time, you might remember the captain who got locked out of his own cockpit inflight due to a scary rant. He'll apparently never fly again, since the judge who released him in 2012 stipulated that he never again try to regain his license.