Keep in mind that DT's original premise was that Sonny went crazy right after his father was shot, that night and the next day or so. I think it's pretty clear that he didn't. Now, we are discussing basic errors that of judgement that Sonny made in the aftermath of his father's attempted murder. That means more than a few days; it means weeks, maybe even months. Those errors I can agree with. So does Vito. Those are the reasons why Vito tells Tom that Sonny was a bad don.