Vieira was reported as saying that United, along with most major clubs in Spain and Italy, benefited from favourable decisions on home soil. The argument has been reignited following Michael Oliver's failure to award Fulham a last-minute penalty at Old Trafford on Monday for Michael Carrick's clumsy challenge on Danny Murphy.
Vieira later claimed the comments were deliberately taken out of context, with the BBC journalist involved banned from the club, but Ferguson thinks there is little to worry about anyway.
Ferguson accepts United - who won the game 1-0 - were lucky with that one. But also pointed out situations this season that saw City benefit from refereeing decisions.
He said: "From the referee's position, I can see why he didn't give a penalty when Danny Murphy was brought down.
"The ball moved to the angle as Michael Carrick challenged him.
"From that position, it wasn't clear. It was a good claim but City could have had a penalty against them at Stoke for a foul by Gareth Barry.
"Every club gets breaks here and there, you get good ones and bad ones. It evens itself out over the season, that will never change."
Ferguson used United's home game against Newcastle in November as an example of a major decision affecting his team, when Rio Ferdinand conceded a penalty for a perfectly fair challenge on Hatem Ben Arfa.
He also has not forgotten how Mario Balotelli escaped a red card for stamping on Scott Parker during Manchester City's win over Tottenham at the Etihad Stadium in January, then scored the match-winning penalty in injury-time.
"We had a terrible decision earlier this season when Newcastle got a penalty and Tottenham could claim the same when Mario Balotelli wasn't sent off and ended up scoring the winning goal," said Ferguson.
"You could go through millions of things like that."