TB you make an excellent point, however Vito didn't kill Sonny because he made intemperate remarks and screewed around with too many women.
...but Sonny didn't actively choose to betray Vito--as Fredo chose to betray Michael.
But I don't disagree with anyone here that Vito would never have had Fredo killed. He had a heart in him. Michael didn't.
I think if there's one overarching message in the Trilogy it's this: Crime doesn't pay. Michael's whole life story was a continuing series of winning battles--and losing wars. It was no one's fault but his.
