I agree that Phil made it too personal. A stand-up guy who we could assume was a major hitter in his day for Carmine Sr, and has killed many brothers, should have taking it on the chin. Butch saw the writing on the wall and took advantage.
You know who is smarter than gets credit, Little Carmine. During the "meeting if the minds", Carmine talked about his friend Rusty getting clipped and he wanted to get to the bottom of it, in time. Then he bought up Billy Leotardo, knowing that was Phil's soft spot. To me he purposefully used that meeting to stir the pot between Phil and Tony.
When the final meeting came about in the warehouse, we gotta assume that Butch and Little Carmine met before that and got on the same page. Phil had to go.