It's a spur of the moment thing - a rush of blood to the head. I've done it myself playing amateur football - a silly pull, push in the back or clipping heels.
The thing is, while he's human, he isn't playing amateur football on a cold Saturday morning after drinking too many pints the night before. He's a professional.
They should know better.
It always seems to be the player you look at at say "yep they'd deffo do it".
Gordon one for us I always expected a challenge like that.