Itachi's wisdom ended at the point he decided it's wise to slaughter his own clan when someone not from his clan told him to do it. There's simply no excuse whatsoever for that. He turned against his own people. How he handled the lone survivor, Sasuke, is inconsequential after that fell deed. It hardly matters what he told or didn't tell Sasuke, the boy's mental health was ruined anyway; it's just semantics to ponder how exactly it was ruined.