Cater isn't expecting Riddle to push him away by the face, but it just serves to make him laugh, giggling merrily as he keeps their arms linked together underneath his jacket. "OMG, Riddle, you're too funny! Today is gonna be a day to remember, that's for sure."

It's as if he wasn't insulted at all. Maybe Cater's just able to tell that yes, it's all coming from a place of embarrassment and not at all malice. He's sure Riddle didn't actually think he was an idiot--and anyway, he does play up the role of the simple fool. There was no point in getting upset for something that he lent purposeful credence to.