Neil protected Gotti and Ruggiero cause Gotti was his protégé. Gotti and Ruggiero were close. Neil was playing referee and trying to have Angelo give up the tapes to end Castellano's breaking his balls. Like Giancarlo said, Paul was probably mad at Angelo and the Gotti's sneaking the drugs on the side. Neil was dying and he knew it, I think he just had enough of Paul's bullshit and decided that "Hey, I am dying, why should I bend backwards anymore for Paul?" I think deep down Neil knew that Gotti was going to eventually kill Paul, if Paul did not go down in the trial.