To the original question: I don't think Fat Tony would have made any difference because, as others have said, Gotti had reason to believe in kill or be killed. But: Gotti and his close circle had reason to think they could get away with the Big Paul hit because the other Dons resented Castellano for disparaging remarks he made about them on tapes the FBI made and released. More important, the Dons were afraid he'd make a deal with the Feds on his RICO rap and rat them out in order to spend his last years with his Colombian house maid and lover, Gloria Olarte.