In addition to being a rat, he's also a hypocrite. In his book, "Underboss," he never fails to denounce Paul Castellano for being a "racketeer," not a "gangster," which is how he flatteringly describes himself and Gotti. But he also never fails to pass along every single compliment Castellano paid him. According to Da Bull, Gotti was the rat, not him, because Gotti betrayed Cosa Nostra "values." (Despite this self-serving B.S., the book is still worth reading. He supplies some riotous descriptions of Gotti's vanities.)