If we're in the middle of an emotional, heated, overly physical game.....and the temperatures off the field are now reaching the point to where adults are screaming at kids and throwing stuff out onto the field.....you don't think there is a chance of that escalating a mob mentality of behaviour on the field? I do.
Also....I don't want or expect a referee to maintain any sort of dialogue whatsoever with parents. In fact...it always annoys me when a referee so obliges the parents.
What I want.......is for the referee to be aware of his/her environment.....and if necessary, warn those off the field if their behaviour is interfering with the integrity of the game. If they do not heed his/her warning he should stop the game until the offending persons are removed from the premises.
Thats not a dialogue. Its taking ownership of what happens and its absolutely the hallmark of a good referee. You can't stop people from acting like jerks and fools. But you can keep it from becoming a part of the game and effecting the game.
In referee training, I was always taught not to do what you are describing. Stop the match and let the coach or school official handle that. Verbal communication with a spectator about their behavior can lead to all sorts of problems.
Ok, then stop the game and talk to the coach and have them enforce proper behaviour. The point is to not allow off the field behaviour to effect the game.