My daughters fellow 05 Bronze team was in a tournament with us, playing a Bronze 04 team, which was much bigger, but lacked some ball skills. The 05 team had a number of 06's guest playing, none of them very physical. The 04 opponent was very physical especially off the ball with pushing, grabbing, elbowing and shoving going on, referee's let them play. One AR had been watching it and just shrugged his shoulders when asked if anything was going to be done, saying what am I supposed to do. It was clearing escalating, getting worse in the second half.
Near the end of the game away from the ball a girl on the other team kicked one of the players from behind when her back was turned, knocking her to the ground. She got up and pushed the girl, then punches were thrown. Parent of the 05 team ran out for his daughter, getting into the face of the other girl, leading to other team parent coming out, etc. Eventually peace was restored. No cards were given out to either girl.
My daughters team played this same 04 team the next day and when the game started to get too rough(illegal rough), the referees used their yellow cards on the different girls which seemed to do the trick keeping the game physical but controlled.
I don't get the "let them play on" philosophy, particularly with the youngers. I get that we don't want to disrupt the game for every little foul and/or injury. I also get that calling everything just leads to players flopping. But when games get out of control, one leading cause is because the refs are letting them play on, a series of minor offenses begin to escalate, soon the parents are getting all angry, and the ref looses control of the game.