The Black Cats progress to round four courtesy of two fantastic second-half goals from Craig Gardner and James McClean but it was the dismissal of Cattermole that left O'Neill with a bitter taste in his mouth.
O'Neill said: "From the minute you start lunging in you are giving the referee no option. It looked from the sideline that the referee had no option.
"I think that whatever we say, we can watch it back a hundred times, the referee is watching someone lunge in and you run that risk, it is crazy."
O'Neill, who has won the League Cup on two occasions as a manager with Leicester, felt Cattermole set a bad example for his team-mates.
"You can't do it, we talked about discipline before the game and there we are, down to 10 men, it is a hard enough battle here and he didn't help himself and he didn't help his team," he said.
"He started the season off brightly for us and he's a great leader - but he has to have discipline himself.
"There is no point asking for discipline from the team when you don't show it yourself."