Normally I would agree, never address the fans, it only encourages them. That being said a coupe of weeks ago I was doing a tournament. I was on the U10 field and due to a shortage of umpires my partner stayed on the same field all tournament. The teams played on 2 fields, so we seen all the teams several times. One "Dad" in particular was very mouthy all weekend, and coaches weren't far behind but they always quieted down just in time*. Anyway the final losers bracket game and Dad is running his mouth as usual from behind the bleachers (we had rain all weekend so few were sitting most were standing behind them)
His daughter bunts down #B line (lines are long gone), I call it foul, close but I feel I was correct. Dad starts jaw jacking. Next pitch is a ball. Next pitch batter bunts again down 3B line. This one was not even as close, Foul Ball.
Dad comes running and screaming to the fence just as I turn to go back behind the plate. I don't know if the fence wasn't there if he would have been right in my face or if he never would have rushed in. My guess is the latter.
Anyway we make eye contact and before I even realize it "SIT DOWN" is coming out of my mouth. Not yelling or loosing it, just sternly. He looks for a second, kinda shocked and just as he starts to say something else he gets another "SIT DOWN" my enunciation is perfect
He turned and went back behind the bleachers and I never heard him say another thing.
I would never advocate addressing the fans, and I was wrong doing so, could have went really bad the other way, but this time it worked out.
*= yes I fully admit I let the coaches go on too much because I have a thick skin, but I also know this hurts other umpires and I am getting better at shutting down a mouthy coach, or removing them form the game.