Ferguson insists Keane was living in a world of fantasy and had lost the respect of his team-mates when he was forced out of Manchester United.
The former manager has used his new autobiography to claim Keane, now a pundit, "thought he was Peter Pan" by the time the pair fell out spectacularly in 2005 and that his departure "was the best thing that could have happened" to United.
His animosity towards Keane has shown no sign of subsiding in the eight years since their row erupted.
Their relationship began to fracture as the midfielder became increasingly outspoken about his team-mates during a lengthy period on the sidelines due to injury and finally broke down when he gave an explosive interview to the club's TV channel.
The now infamous MUTV interview has never been aired on the channel but Ferguson claim that Edwin Van der Sar, Paul Scholes and Ruud van Nistelrooy were among the players who walked out when they were shown it privately.
The 71-year-old recalls Keane and Van Nistelrooy having to be pulled apart in a separate incident: "His [Keane's] eyes started to narrow, almost to wee black beads. It was frightening to watch, and I'm from Glasgow."
But after the MUTV interview, Ferguson says he could not get Keane out quickly enough. He told his assistant, Carlos Queiroz, at the time: "He needs to go, Carlos. 100 per cent. Get rid of him."
Ferguson, in his book, said: "In one deep sense, him leaving was the best thing that could have happened, because a lot of players were intimidated by him."
Keane was responded on ITV on Tuesday night by saying: "I'm okay, quite relaxed. I remember having conversations about loyalty when I was at the club and I don't think he knows the meaning of the word.
"To constantly criticise other players that brought him success...I won't be losing any sleep over it.
"I just don't think the manager needs to do it. I don't know how many books he's written now. A lot of these players helped win a lot of trophies. It's just part of modern life. People like to do books and criticise ex-players.
"I'll have to do another book!"