Love life aside, Paolo was bothered that Tony, who's wife after all he was screwing, was entertaining changing notions about who might've been responsible for his brother's death. Everyone in the organisation was a suspect and Paolo's own immunity could be called into question at any time.
There was danger in pointing a finger at anyone else in the organisation in that, like Franco, it might come back to bite Paolo. He had to get very close to Tony again and try to get him thinking of external rivals. There was no shortage of gang bosses with grudges out there.