A head butt albeit a little one, is still a head butt. Maybe the Gent player didn't touch his opponent with his head, but it looked mean and was intended so too. Paixao waved it off. What's a little head butting among gentlemen...
when he let the headbutter go, all players seem to have lost their respect for the referee: he couldn't even get the attention when he wanted to show his yellow card. Paixao had to go look for the culprit, he touched his back, the player didn't turn, then the Portuguese ref grabbed the player's arm and pulled him away from the others. Read that again: he had to pull the player away to get his attention. I rest my case.