A poor first half of the season has led to speculation the Red Devils might dismiss the Scot after less than a year, but his predecessor thinks this would be a big mistake.
United has struggled in Moyes' first campaign as manager and sits seventh in the Premier League after 22 rounds with 11 wins, four draws and seven defeats.
The reigning Premier League champion has also been eliminated from both the FA and Capital One Cups, although the club remains alive in the Champions League.
United's poor results and form have led to speculation the perennial league contender will sack Moyes less than a year into his six-year contract.
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But Ferguson cannot understand the culture of sacking managers and believes most need time to achieve success at new clubs.
"I can never understand why clubs change managers so quickly," the 72-year-old told BBC Sport. "They [board members] must discuss the qualities of the manager they are going to offer the job to [and] you must look at his CV – the character, the philosophy he has, surely.
"Now if that is the way they have gone about giving the man the job, why don't they persist with it? It seems so stupid to me. There is no need to go down that road [of sacking managers]. United can do anything. They have got that great philosophy and history, they will always do well."
When Ferguson took over at Old Trafford, he had won 10 major trophies with Aberdeen in the Scottish First Division but it took him six seasons to win the league in England.
United finished 11th, second, 11th, 13th, sixth and second before Ferguson notched his first league title with the club during the 1992-93 season.
Twelve more league titles followed before Ferguson retired at the end of last term - after again leading United to the championship - but the club director believes he has never seen a season like the 2013-14 Premier League campaign.
"This year for the first time it really looks as if five or six could be involved [in the title race], so it's a great Premier League," Ferguson said. "It's still not an easy league to win. I think the English game is the most honest and is the hardest league to win in terms of the competition you face. You can lose to anyone."