I have not played competitively in many years but shirt pulling has become endemic in today's game. When I played, if there was obvious shirt pulling like that to gain an advantage you would have been sent off. Any egregious professional foul, and it didn't matter where on the field it was, you were gven your marching orders. Now it seems that in most cases, it's denial of an obvious scoring opportunity that results in a red. Shirt pulling was not as common back then ...now refs turn a blind eye to it, and it ends up being a complete clusterfuck in the box when there is a free kick etc. It's one of the things that has really turned me off 'modern" football. I think for most players, if you are trying to go past an opposing player who is pulling the shirt of your back, the natural reaction is lashing your arm back to try and break free. Then it gets into violent conduct territory.