For this he called, it was clear what he was doing. He should know better then flipping and he should be reminded not to do it. It causes problems. Had he flipped say a KX, then I would of called it a fold. Your not allowed to expose cards untill all betting is completed. I was at a tournement at a casino and they have the following rule.
If in heads up play, all cards deaqlt and player a goes all in and player B flips up his cards to get a read on player A. Then player A would have to sit out of the game for 30 minutes while still paying the blinds. The second time time it happens, he is thrown out of the tournement.