The Italian appeared to goad fans and was involved in altercation with Rio Ferdinand and Anderson, but veteran says he just got carried away in the heat of the moment
The 20-year-old striker goaded fans of the defeated side by thrusting the City badge in their direction and provoked United pair Anderson and Rio Ferdinand, with the trio having to be separated by team-mates.
However, former Arsenal man Vieira, who also played with Balotelli at Inter, claims that the youngster was not acting out of malice, just exuberance.
"That's part of his personality, that's Balotelli's charm," the Frenchman said.
"I don't think it was a case of provocation, I just think he got carried away.
"There was more pressure on City's shoulders than United's. As a club and as a team, United are more used to controlling these types of games.
"For us, it was pure joy because the club has been waiting for this for so long," Vieira added. "And with all the press expecting United to win easily, it was a big relief.
"There was some over-excitement, but I think United's players got carried away as well."
Ferdinand, who criticised the youngster for celebrating in front of the United fans, apologised for his part in the post-match scuffle on Twitter, saying: "If I offended anyone I apologise, emotions obviously running high."