He reckons ref Phil Dowd made a "crazy" decision to caution the player at Arsenal on Sunday - a yellow card which led to a one-match ban.
O'Neill insisted: "It was far too close to call for simulation, it was crazy.
"Alex Song may or may not have touched him - no one can be certain about that. But to book him was utter lunacy. Referees will gather and think it was a dive.
"Ashley gets very close to players who are going to get a foot in and get a touch. That is an art."