I have seen this, but I am glad you have too. This is an absolute disgrace, should never be like this, should and will be controlled in the future. Fair enough shouting "lets go" or "sit down" but publicly demoralising someone using foul words, while looking as if they are starting a fight, is wrong on so many levels. The video in all fairness did not touch on the sportsmanship that takes place after games at all, everyone shakes hands and are friends out of games, but it doesn't allow for that behaviour. As you saw it was only 3 teams that do this, everyone else in the community acknowledges the public eye is on them when playing, therefore they act professionally for their own image, the event organisers image and the community's image. To summarise it is only a select few teams that act as if they are in gang land territory when playing at events, sorry you had to witness that mate.
