There are a lot of field with these signs in Australia - my hockey fields all have them.

And yes, sometimes you have to cool someone down on or off the field. I used to be the person calming the hothead on our team (a fifteen year old with a strong sense of justice) when we got a call she felt was unfair. (Sorry kiddo, sometimes the dice just fall shitwise.)

Thankfully, I wasn't the person trying to rein in a former coach (who was...not great with the encouragement) - that fell to our captain at the time, who was an absolute trooper...