Italian boss Mancini made the gesture following a handball offence committed by Wigan defender Maynor Figueroa, who was eventually booked for the incident.
McCarthy accepts that there may be cultural differences present, but insists that Mancini should abide by the spirit of the English game.
"None of us should do it," he told reporters. "It is something I don't like. There is a cultural difference. Roberto is in this country now.
"It is a little blip on a really good career for him at Man City because he handles himself with such good dignity and grace.
"I don't think anyone should do it. It is wrong. It looks bad and I'm sure if it is pointed out, Roberto won't do it again."