Ronaldo was very unhappy at the United bench after being replaced by Paul Scholes on the hour mark in the win over Manchester City.
Robson told Goal.com: “It’s not right for players to react to their manager’s decision. Players do respond differently but they have to respect the decision of the manager, especially when it comes from someone like Sir Alex Ferguson.
“He knows what’s right for the players, to ensure that the player stays fresh and doesn’t get injured ahead of the next clash.
“I feel Ronaldo’s reaction was wrong and it sent a wrong lesson to the kids watching the game around the world.”