Unfortunately, these kids have learnt that from somebody. Lots of somebodies. Kids follow, or copy, what they know. The sad thing is, anyone joining those teams who doesn't behave like that either won't get a game or will incur the wrath of the herd. You see it in every sport, and it doesn't start with the kids. I've been lucky enough to have been a parent on a team (soccer) where everyone was supportive and the kids all had fun. To see them grow and gel as a team over 3 years was an absolute joy. No coincidence that our team had more supporters than our opposition, week in, week out. Win, lose or draw, our kids learnt a lot about life, particularly when they were getting kicked behind play and learning that retaliation doesn't pay! BTW - takes a special person to be a referee. Hope this experience doesn't sour it for you.